:: wikimiki.org ::

Pubarche

Pubarche

Pubarche refers to the first appearance of pubic hair in a child. Pubarche is one of the physical changes of puberty but should not be equated with it since it may occur independently of complete puberty. Pubarche usually results from rising levels of androgens from the adrenal glands or testes but may also result from exposure of a child to an anabolic steroid. When pubarche occurs prematurely (in early or mid-childhood), it is referred to as premature pubarche and may warrant an evaluation. Premature adrenarche is the most common cause of premature pubarche. Rarer causes include precocious puberty, congenital adrenal hyperplasia, and androgen-producing tumors of the adrenals or gonads. When adrenarche, central puberty, and all pathologic conditions have been excluded, the term isolated premature pubarche is used to describe the unexplained development of pubic hair at an early age without other hormonal or physical changes of puberty. See also puberty, adrenarche, androgens

Pubic hair

Pubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region. Although fine vellus hair is present in the area in childhood, the term pubic hair is generally restricted to the heavier, longer hair that develops with puberty as an effect of rising levels of androgens on the skin of the genital area

Development of pubic hair

Before puberty, the genital area of both boys and girls has very fine vellus hair, referred to as Tanner stage 1 hair. In response to rising levels of androgens as puberty begins, the skin of the genital area begins to produce thicker, often curlier, hair with a faster growth rate. The onset of pubic hair development is termed pubarche. The change for each hair follicle is relatively abrupt, but the extent of skin which grows androgenic hair gradually increases over several years. In most girls, pubic hair first appears along the edges of the labia majora (stage 2), and spreads forward to the mons (stage 3) over the next 2 years. By 3 years into puberty (roughly the time of menarche for most girls), the pubic triangle is densely filled. Within another 2 years pubic hair also grows from the near thighs in most young women, and sometimes a small amount up the line of the abdomen toward the umbilicus. In boys, the first pubic hair appears as a few sparse hairs on the scrotum or at the upper base of the penis (stage 2). Within a year, hairs around the base of the penis are too numerous to count (stage 3), and within 3 to 4 years, hair fills the pubic area (stage 4), and by 5 years extends to the near thighs and upwards on the abdomen toward the umbilicus (stage 5). Other areas of the skin are similarly, though slightly less, sensitive to androgens and androgenic hair typically appears somewhat later. In rough sequence of sensitivity to androgens and appearance of androgenic hair, are the armpits (axillae), perianal area, upper lip, preauricular areas (sideburns), periareolar areas (nipples), middle of the chest, neck under the chin, remainder of chest and beard area, limbs and shoulders, back, and buttocks. Although generally considered part of the process of puberty, pubarche is distinct and independent of the process of maturation of the gonads that leads to sexual maturation and fertility. Pubic hair can develop from adrenal androgens alone, and can develop even when the ovaries or testes are defective and nonfunctional. See puberty for details. There is little if any difference in the capacity of male and female bodies to grow hair in response to androgens. The obvious sex-dimorphic difference in hair distribution in men and women is primarily a result of differences in the levels of androgen reached as maturity occurs.

Variations

Patterns of pubic hair vary among people. On some people, pubic hair is thick and/or coarse, while on others it may be sparse and/or fine. Pubic hair and axillary (armpit) hair can vary in color considerably from the hair of the scalp. In most people it is darker, although it can also be lighter. On many men, pubic hair color is closest to the color of their beards (before their beards start turning white with age), which again can vary from the color of the hair on top of the head. On most women, the pubic patch is triangular and lies over the mons veneris, or mound of Venus. On many men, the pubic patch tapers upwards to a line of hair pointing towards the navel. As with axillary (armpit) hair, pubic hair is associated with a concentration of sebaceous glands in the area. Like other hair, pubic hair may be infested by lice, with a specific category of pubic lice.

Purpose of pubic hair

It is believed that the functions of pubic hair include the dissemination of pheromones, protection from the friction of sexual intercourse; natural selection may also have sustained it insofar as it can symbolize sexual maturity to a potential sexual partner. Pubic hair and the growth between the tops of the legs and the buttocks, like under arm hair, helps to lubricate the areas, making movement smoother and more comfortable.

Cultural

Attitudes

Attitudes toward pubic hair are similar to those regarding axillary (armpit) hair in that cultural and personal norms can be reflected in reactions ranging from pleasure to revulsion, both for the presence and absence of such hair. As with any sexually charged matter there are persons of both sexes who have strong points of view toward the culturally related issues associated with presence or lack of body hair. points of view In Japanese drawings pubic hair is often omitted for legal reasons (see hentai), as for a long time the display of pubic hair was not legal. The interpretation of the law has since changed. In Islamic societies, removing the pubic hair is a religiously endorsed hygiene practice, ranked along with circumcision, clipping the fingernails, brushing the teeth, etc. In Western societies since the 1960s it has become increasingly common to trim or completely remove pubic hair. In some Asian societies, such as Korea, a lack of natural pubic hair is sometimes common. In contrast against current Western trends, in these cultures excess pubic hair is often seen as highly desirable. Some have gone as far as having hair surgically transplanted from their head to the genital area to attain the desired amount. [http://www.ishrs.org/articles/hair-east-asians.htm] Before the twentieth century, fine-art paintings and sculpture in the Western tradition usually depicted women without either pubic hair or a visible vulva. John Ruskin, the famous author, artist, and art critic, was apparently accustomed to these depictions and unaware of the actual appearance of nude women. On his wedding night, he was allegedly so shocked by his discovery of his wife Effie's pubic hair that he rejected her, and the marriage was legally annulled. Francisco Goya's The Nude Maja was probably the first European painting to show woman's pubic hair, though others had hinted at it. Some common slang includes bush, muff, curlies, pubes.

Modification of pubic hair

Trimming or completely removing pubic hair has become a custom in many cultures. A preference for hairless genitals is known as acomoclitism. The methodology of removing hair is called depilation (when removing only the hair above the skin) or epilation (when removing the entire hair). The trimming or removal of body hair by men is sometimes referred to as manscaping.

Reasoning

Some arguments for modification of pubic hair have included:
- hygiene, especially during menstruation
- aesthetic
- tradition
- religious
- sexual practice, such as BDSM cultures or for oral sex

Removal methods

Pubic hair is usually removed or reduced by shaving, but often for more long-term removal, waxing or use of a mechanical device is used to pull the hair out at the root. Methods to remove pubic hair include:
- Shaving - uses a razor (straight razor, safety razor, or electric razor) to cut the hair at the level of the skin (or very close to it)
- Epilators - these electric devices use rotating coils to pull the hairs out by the roots
- Laser epilation and Intense pulsed light (IPL)
- Waxing and Sugaring - Some hair salons in France offer what is called "epilé complet" which is the removal of all pubic hair using hot wax.
- Hair removal creams and lotions
- Electrology - involves using a current of electricity down the length of the hair to kill the hair root
- Hair Growth Inhibitors - these lotions claim to slow the hair growth and even prevent its growth but they have had limited success
- Tweezers - this is a manual method usually done to remove any remaining hairs after use of the other treatments. Note that:
- Electrical razors are a little safer and do not shave off skin along with the hair.
- Shaving can cause skin irritation (pseudofolliculitis barbae, or "razor bumps") and hair getting locked under the skin area.
- Hair re-growth can sometimes be uncomfortable and itchy, although continued removal reduces this effect.
- Using hair removal creams or lotions in the pubic and chest areas is not advisable, as it may result in serious skin irritations. (See the [http://www.euronaturist.com/smooth.htm Smooth Naturist] webpage for more advice on pubic shaving)

Style

The modification of pubic hair can also be considered a statement about one's style or personal lifestyle. The fashion designer Mary Quant was famously proud that her husband trimmed hers into a heart shape. In the 1930s the louche Baron Martin Stillman von Brabus shaved the pubic hair of his lover Margaret, Duchess of Argyll into a representation of the Mercedes-Benz 3-pointed star. Some common styles include:
- Bikini waxing - trimming the sides of the triangle so that pubic hair cannot be seen while wearing swimwear (either gender)
- Strip - removing hair from both sides of labia majora, leaving a strip (females) sometimes called a "landing strip"
- Brazilian Waxing - removing all pubic hair, or (less commonly) removing all except a small patch, line, or triangle over the clitoris or penis

External links

- [http://www.artnet.com/magazine/features/saltz/saltz4-10-02.asp Pudenda Agenda] - From artnet.com
- [http://www.hairchick.com/pubic-hair-removal.php Pubic Hair Removal] Category:Integumentary system Category:Human appearance Category:Secondary sexual characteristics als:Schamhaar ja:陰毛

Puberty

Puberty refers to the process of physical changes by which a child's body becomes an adult body capable of reproduction. Growth accelerates in the first half of puberty and reaches completion by the end. Body differences between boys and girls before puberty are almost entirely restricted to the genitalia. During puberty, major differences of size, shape, composition, and function develop in many body structures and systems. The most obvious of these are referred to as secondary sexual characteristics. In a strict sense, the term puberty (and this article) refer to the bodily changes of sexual maturation rather than the psychosocial and cultural aspects of adolescent development. Adolescence is the period of psychological and social transition between childhood and adulthood. Adolescence largely overlaps the period of puberty but its boundaries are less precisely defined and it refers as much to the psychosocial and cultural characteristics of development during the teen years as to the physical changes of puberty.

Puberty as a physical process

Physical changes of puberty in girls

Breast development

The first physical sign of puberty in girls is usually a firm, tender lump under the center of the areola(e) of one or both breasts, occurring on average at about 10.5 years. This is referred to as thelarche. By the widely used Tanner staging of puberty, this is stage 2 of breast development (stage 1 is a flat, prepubertal breast). Within 6-12 months, the swelling has clearly begun in both sides, softened, and can be felt and seen extending beyond the edges of the areolae. This is stage 3 of breast development. By another 12 months (stage 4), the breasts are approaching mature size and shape, with areolae and papillae forming a secondary mound. In most young women, this mound disappears into the contour of the mature breast (stage 5), although there is so much variation in sizes and shapes of adult breasts that distinguishing advanced stages is of little clinical value.

Pubic hair in girls

Pubic hair is often the second unequivocal change of puberty. It is referred to as pubarche and the pubic hairs are usually visible first along the labia. The first few hairs are described as Tanner stage 2. Stage 3 is usually reached within another 6–12 months, when the hairs are too numerous to count and appear on the mons as well. By stage 4, the pubic hairs densely fill the "pubic triangle." Stage 5 refers to spread of pubic hair to the thighs and sometimes upward towards the umbilicus. In about 15% of girls, the earliest pubic hair appears before breast development begins.

Vagina, uterus, ovaries

The mucosal surface of the vagina also changes in response to increasing levels of estrogen, becoming thicker and a duller pink in color (in contrast to the brighter red of the prepubertal vaginal mucosa). Whitish secretions (physiologic leukorrhea) are a normal effect of estrogen as well. In the next 2 years following thelarche, the uterus and ovaries increase in size. The ovaries usually contain small cysts visible by ultrasound.

Menstruation and fertility

The first menstrual bleeding is referred to as menarche. The average age of menarche is about 12.7 years, usually about 2 years after thelarche. Menses (menstrual periods) are not always regular and monthly in the first 1–2 years after menarche. Ovulation is necessary for fertility, and may or may not accompany the earliest menses. By 2 years after menarche, over 90% of girls are experiencing very regular, predictable menses accompanied by ovulation. Continued irregularity after 2 years from menarche usually predicts prolonged irregularity and anovulation. The word nubility has been proposed academically to designate achievement of fertility.

Pelvic shape, fat distribution, and body composition

During this period, also in response to rising levels of estrogen, the lower half of the pelvis widens (providing a larger birth canal). Fat tissue increases to a greater percentage of the body composition than in males, especially in the typical female distribution of breasts, hips, and thighs. This produces the typical female body shape.

Body and facial hair in girls

In the months and years following the appearance of pubic hair, other areas of skin which respond to androgens develop heavier hair in roughly the following sequence: underarm (axillary) hair, perianal hair, upper lip hair, sideburn (preauricular) hair, and periareolar hair. Arm and leg hair becomes heavier more gradually over 10 years or more. Although in Western culture, hair in some of these areas is unwanted, it rarely indicates a hormone imbalance unless it occurs elsewhere as well (such as under the chin and in the midline of the chest).

Height growth in girls

The estrogen-induced pubertal growth spurt in girls begins at the same time the earliest breast changes begin, or even a few months before, making it one of the earliest manifestations of puberty in girls. Growth of the legs and feet accelerates first, so that many girls have longer legs in proportion to their torso in the first year of puberty. The rate of growth tends to reach a peak velocity (as much as 7.5-10 cm or 3-4 inches per year) midway between thelarche and menarche and is already declining by the time menarche occurs. In the 2 years following menarche most girls grow about 5 cm (2 inches) before growth ceases at maximal adult height. This last growth primarily involves the spine rather than the limbs.

Body odor, skin changes, and acne

Rising levels of androgens can change the fatty acid composition of perspiration, resulting in a more "adult" body odor. This often precedes thelarche and pubarche by 1 or more years. Another androgen effect is increased secretion of oil (sebum) from the skin. This change increases the susceptibility to acne, a characteristic affliction of puberty greatly variable in its severity.

Physical changes of puberty in boys

Testicular size, function, and fertility

In boys, testicular enlargement is the first physical manifestation of puberty (and is termed gonadarche). Testes in prepubertal boys change little in size from about 1 year of age to the onset of puberty, averaging about 2–3 cc in volume and about 1.5-2 cm in length. Testicular size continues to increase throughout puberty, reaching maximal adult size about 6 years later. While 18-20 cc is reportedly an average adult size, there is wide variation in the normal population. The testes have two primary functions: to produce hormones and to produce sperm. The Leydig cells produce testosterone (as described below), which in turn produces most of the changes of male puberty. However, most of the increasing bulk of testicular tissue is spermatogenic tissue (primarily Sertoli and interstitial cells). The development of sperm production and fertility in males is not as well documented. Sperm can be detected in the morning urine of most boys after the first year of pubertal changes (and occasionally earlier).

Genitalia

A boy's penis grows little from the fourth year of life until puberty. Average prepubertal penile length is 4 cm. The prepubertal genitalia are described as Tanner stage 1. Within months after growth of the testes begins, rising levels of testosterone promote growth of the penis and scrotum. This earliest discernible beginning of pubertal growth of the genitalia is referred to as stage 2. The penis continues to grow until about 18 years of age, reaching an average adult size of about 7-14 cm. Although erections and orgasm occur in prepubertal boys, they become much more common during puberty, accompanied by a markedly increased libido. Ejaculation becomes possible early in puberty; prior to this boys may experience dry orgasms. Emission of seminal fluid may occur due to masturbation or spontaneously during sleep (commonly termed a wet dream, and more clinically called a nocturnal emission). The ability to ejaculate is a fairly early event in puberty compared to the other characteristics. However, in parallel to the irregularity of the first few periods of a girl, for the first one or two years after a boy's first ejaculation, his seminal fluid may contain few active sperm.

Pubic hair in boys

Pubic hair often appears in a boy shortly after the genitalia begin to grow. As in girls, the first appearance of pubic hair is termed pubarche and the pubic hairs are usually first visible at the dorsal (abdominal) base of the penis. The first few hairs are described as Tanner stage 2. Stage 3 is usually reached within another 6–12 months, when the hairs are too numerous to count. By stage 4, the pubic hairs densely fill the "pubic triangle." Stage 5 refers to spread of pubic hair to the thighs and upward towards the umbilicus.

Body and facial hair in boys

In the months and years following the appearance of pubic hair, other areas of skin which respond to androgens develop heavier hair in roughly the following sequence: underarm (axillary) hair, perianal hair, upper lip hair, sideburn (preauricular) hair, periareolar hair, and the rest of the beard area. Arm, leg, and back hair become heavier more gradually. There is a large range in amount of body hair among adult men, and significant differences in timing and quantity of hair growth among different ethnic groups.

Voice change

Under the influence of androgens, the voice box, or larynx, grows in both genders. This growth is far more prominent in boys, causing the male voice to drop, rather abruptly, about one octave, probably because the larger vocal folds have a lower fundamental frequency. Occasionally, this is accompanied by cracking and breaking sounds in the early stages. Most of the voice change happens during stage 4 of male puberty around the time of peak growth. However, it usually precedes the development of significant facial hair by several months to years.

Height growth in boys

Compared to girls' early growth spurt, growth accelerates more slowly in boys and lasts longer, resulting in a taller adult stature among males than females (on average about 10 cm or 4 inches). The difference is attributed to the much greater potency of estradiol compared to testosterone in promoting bone growth, maturation, and epiphyseal closure. In boys, growth begins to accelerate about 9 months after the first signs of testicular enlargement and the peak year of the growth spurt occurs about 2 years after the onset of puberty, reaching a peak velocity of about 8.5–12 cm or 3.5–5 inches per year. The feet and hands experience their growth spurt first, followed by the limbs, and finally ending in the trunk. Epiphyseal closure and adult height are reached more slowly, at an average age of about 17.5 years. As in girls, this last growth primarily involves the spine rather than the limbs.

Male musculature and body shape

By the end of puberty, adult men have heavier bones and nearly twice as much skeletal muscle. Some of the bone growth (e.g., shoulder width and jaw) is disproportionately greater, resulting in noticeably different male and female skeletal shapes. The average adult male has about 150% of the lean body mass of an average female, and about 50% of the body fat. This muscle develops mainly during the later stages of puberty, and muscle growth can continue even after a male is biologically adult. The peak of the so-called "strength spurt," the rate of muscle growth, is attained about one year after a male experiences his peak growth rate.

Body odor, skin changes, acne

Rising levels of androgens can change the fatty acid composition of perspiration, resulting in a more "adult" body odor. As in girls, another androgen effect is increased secretion of oil (sebum) from the skin and the resultant variable amounts of acne.

Breast development in boys: pubertal gynecomastia

Estradiol is produced from testosterone in male puberty as well as female, and male breasts often respond to the rising estradiol levels. This is termed gynecomastia. In most boys, the breast development is minimal, similar to what would be termed a "breast bud" in a girl, but in many boys, breast growth is substantial. It usually occurs after puberty is underway, may increase for a year or two, and usually diminishes by the end of puberty. It is increased by extra adipose tissue if the boy is overweight. Although this is a normal part of male puberty for perhaps half of boys, breast development is usually as unwelcome as upper lip hair in girls, and can be removed surgically if the boy's distress is substantial.

Variations of normal puberty

Typical puberty is described above, but many children vary with respect to timing of onset, tempo, steadiness of continuation, and sequence of events.

Timing of onset

Puberty is a process with a gradual onset beginning with changes of neuronal function in the hypothalamus, resulting in rising hormonal signals between brain and gonads, proceeding to gonadal growth and production of sex steroids, which in turn induce changes in responsive parts of the body. The definition of onset, therefore, depends on the perspective (e.g., hormonal versus physical) and purpose (establishing population normal standards, clinical care of early or late children, or a variety of other social purposes). The most commonly used definition of onset for both social and medical purposes is the appearance of the first physical changes described in this section of this article, but the reader should understand that they are a result of preliminary neural, hormonal, and gonadal function changes that are usually impossible or impractical to detect. The age at which puberty begins can vary widely between individuals. Timing of onset is affected by genetic factors, body mass and nutritional state, and general health. Timing may also be affected by environmental factors (exogenous hormones and environmental substances with hormone-like effects) and there is even weak evidence that life experiences may play a role as well. Ethnic/racial differences have been recognized for centuries, although many of them may be attributable to confounding environmental and socioeconomic factors (such as weight). Average age for first signs of breast development in girls is about 10.5 years. Average age for first signs of testicular enlargement in boys is 11.5 years. See Tables below for approximate average ages and ranges for other milestones of physical development of North American children. Duration of puberty (time from onset to completion) varies less between children than does the age of onset. Duration of puberty in girls from onset of breast development to cessation of growth is roughly 5 years. Duration of puberty in boys from first testicular enlargement to cessation of growth is about 6 years. Table 1 provides 3rd, 50th, and 97th percentiles for attainment of selected stages by American girls as reported in 1985. In these tables, B, PH, and G refer to the Tanner stages of physical puberty: B is breast, PH is pubic hair, and G is genitalia (penis and testes). B1, PH1, and G1 are the prepubertal stages of each of these, while B2, PH2, and G2 are the earliest signs of puberty. B5, PH5, and G5 are adult stages at the end of puberty. The Tanner stage article contains links to fuller explanations of the specific stages. All three tables below express ages as years and months (y and m).

Table 1: Ages of attainment of pubertal stages of American girls

3rd %ile 50th %ile 97th %ile B2 8y 10m 10y 11m 13y 0m B3 9y 10m 11y 11m 14y 0m B4 10y 6m 12y 11m 15y 5m PH2 9y 0m 11y 3m 13y 6m PH3 9y 8m 11y 11m 14y 3m PH4 10y 5m 12y 7m 14y 11m Menarche 10y 10m 12y 9m 14y 7m Peak height velocity 9y 0m 11y 6m 14y 0m However, a later survey from a group of American primary pediatric practices reported both a slightly earlier average onset, greater range, and more importantly, a significant difference between white and African-American girls at some stages (Table 2).

Table 2: Recent survey on American girls by race

White girls 3rd %ile 50th %ile 97th %ile B2 6y 5m 10y 0m 13y 7m B3 8y 7m 11y 4m 14y 1m B4 10y 4m 12y 9m 15y 3m B5 11y 4m 14y 6m 17y 9m PH2 7y 2m 10y 5m 13y 8m PH3 8y 8m 11y 5m 14y 2m PH4 10y 5m 12y 7m 14y 9m PH5 12y 5m 14y 7m 16y 8m Menarche 10y 6m 12y 10m 15y 3m Peak height velocity 10y 12y 2m 14y African-American 3rd %ile 50th %ile 97th %ile B2 5y 0m 8y 11m 12y 10m B3 7y 7m 10y 2m 12y 11m PH2 4y 9m 8y 9m 12y 9m PH3 7y 6m 10y 3m 13y 0m Menarche 9y 10m 12y 2m 14y 6m

Table 3: Ages of attaining stages of puberty for American boys

3rd % 50th % 97th% PH2 9y 11m 12y 0m 14y 1m PH3 11y3m 13y 1m 14y 11m PH4 12y 0m 13y 10m 15y 9m G2 9y 3m 11y 6m 13y 9m G3 10y 2m 12y 4m 14y 8m G4 11y 3m 13y 3m 15y 5m Testicular size 4 cc or 2.5 cm 9y 6m 11y 6m 13y 6m 6 cc or 3 cm 10y 2m 12 cc or 3.6 cm 11y 6m 14y 0m 16y 6m 15 cc or 3.8 cm 16y 6m Peak height velocity 11y 13y 6m 15y 8m

Variations of tempo and progression

Tempo is the speed at which the process of pubertal changes progresses from beginning to end. The duration of puberty generally varies less than timing of onset, and approximates 4 years for girls and 6 for boys (from first physical changes to attainment of adult height). Nevertheless, some healthy children can proceed through puberty at a faster or slower tempo than most. An interruption of progression of puberty is usually, but not always, due to abnormal causes such as malnutrition or anorexia nervosa. Perhaps the most common apparently healthy variation is apparent interruption for a couple of years just after attainment of an early sign of initiation. For instance, some girls may seem to develop stage 2 breast buds at 6 or 7 years of age with no other signs of puberty, and nothing may happen for 2 or 3 years. Physicians refer to this as "unsustained puberty."

Variations of sequence

The sequence of events of pubertal development can occasionally vary. For example, in about 15% of boys and girls, pubarche (the first pubic hairs) can precede, respectively, gonadarche and thelarche by a few months. Rarely, menarche can occur before other signs of puberty in a few girls. These variations deserve medical evaluation because they can occasionally signal a disease.

Conclusion of puberty

In a general sense, the conclusion of puberty is reproductive maturity. Criteria for defining the conclusion may differ for different purposes: attainment of the ability to reproduce, achievement of maximal adult height, maximal gonadal size, or adult sex hormone levels. Maximal adult height is achieved at an average age of 14.5 years for American girls and 17.5 years for American boys. Potential fertility (sometimes termed nubility) usually precedes completion of growth by 1-2 years in girls and 3-4 years in boys. Stage 5 in the tables above typically represents maximal gonadal growth and attainment of adult hormone levels.

Puberty as a hormonal process

The endocrine reproductive system consists of the hypothalamus, the pituitary, the gonads, and the adrenal glands, with input and regulation from many other body systems. The simplest description of hormonal puberty is the following: #The brain's hypothalamus begins to release pulses of GnRH. True puberty is often termed "central puberty" because it begins as a process of the central nervous system. #Cells in the anterior pituitary respond by secreting LH and FSH into the circulation. #The ovaries or testes respond to the rising amounts of LH and FSH by growing and beginning to produce estradiol and testosterone. #Rising levels of estradiol and testosterone produce the body changes of female and male puberty. The onset of this neurohormonal process may precede the first visible body changes by 1-2 years but is rarely detected in individual children.

Components of the endocrine reproductive system

The arcuate nucleus of the hypothalamus is the driver of the reproductive system. It has neurons which generate and release pulses of GnRH into the portal venous system of the pituitary gland. The arcuate nucleus is affected and controlled by neuronal input from other areas of the brain and hormonal input from the gonads and a variety of other systems. The pituitary gland responds to the GnRH pulses by releasing LH and FSH into the blood of the general circulation, also in a pulsatile pattern. The gonads (testes and ovaries) respond to rising levels of LH and FSH by producing the steroid sex hormones, testosterone and estradiol. The adrenal glands are a second source for steroid hormones. Adrenal maturation, termed adrenarche, typically precedes gonadarche in mid-childhood.

Major hormones of puberty

- GnRH (gonadotropin-releasing hormone) is a peptide hormone released from the hypothalamus which stimulates gonadotrope cells of the anterior pituitary.
- LH (luteinizing hormone) is a larger protein hormone secreted into the general circulation by gonadotrope cells of the anterior pituitary. The main target cells of LH are the Leydig cells of testes and the theca cells of the ovaries. LH seems to play a larger role in the initiation of puberty than FSH, as levels increase about 25-fold with the onset of puberty, compared with the 2.5-fold increase of FSH.
- FSH (follicle stimulating hormone) is a peptide hormone secreted into the general circulation by the gonadotrope cells of the anterior pituitary. The main target cells of FSH are the ovarian follicles and the Sertoli cells and spermatogenic tissue of the testes.
- Testosterone is a steroid hormone produced primarily by the Leydig cells of the testes, and in lesser amounts by the theca cells of the ovaries and the adrenal cortex. Testosterone is the primary mammalian androgen and the "original" anabolic steroid. It acts on androgen receptors in responsive tissue throughout the body.
- Estradiol is a steroid hormone produced by aromatization of testosterone. Estradiol is the primary human estrogen and acts on estrogen receptors throughout the body. The largest amounts of estradiol are produced by the granulosa cells of the ovaries, but lesser amounts are derived from testicular and adrenal testoterone.
- Adrenal androgens are steroids produced by the zona reticulosa of the adrenal cortex in both sexes. The major adrenal androgens are dehydroepiandrosterone, androstenedione (which are precursors of testosterone), and dehydroepiandrosterone sulfate which is present in large amounts in the blood. Adrenal androgens contribute to the androgen events of early puberty in girls.
- IGF1 (insulin-like growth factor 1) rises substantially during puberty in response to rising levels of growth hormone and may be the principal mediator of the pubertal growth spurt.
- Leptin is a protein hormone produced by adipose tissue. Its primary target organ is apparently the hypothalamus. The leptin level seems to provide the brain a rough indicator of adipose mass for purposes of regulation of appetite and metabolism. It also plays a permissive role in female puberty, which usually will not proceed until an adequate body mass has been achieved.

The process of puberty from an endocrine perspective

The endocrine reproductive system becomes functional by the end of the first trimester of fetal life. The testes and ovaries become briefly inactive around the time of birth but resume hormonal activity until several months after birth, when incompletely understood mechanisms in the brain begin to suppress the activity of the arcuate nucleus. This has been referred to as maturation of the prepubertal "gonadostat," which becomes sensitive to negative feedback by sex steroids. Gonadotropin and sex steroid levels fall to low levels and remain nearly undetectable for approximately another 8-10 years of childhood. Evidence is accumulating that the reproductive system is not totally inactive during the childhood years. Subtle increases in gonadotropin pulses occur, and ovarian follicles surrounding germ cells (which will become eggs) double in number. Normal puberty is initiated in the hypothalamus, with de-inhibition of the pulse generator in the arcuate nucleus. This inhibition of the arcuate nucleus is an ongoing active suppression by other areas of the brain. The signal and mechanism releasing the arcuate nucleus from inhibition have been the subject of investigation for decades and remain incompletely understood. Leptin levels rise throughout childhood and play a part in allowing the arcuate nucleus to resume operation. If the childhood inhibition of the arcuate nucleus is interrupted prematurely by injury to the brain, it may resume pulsatile gonadotropin release and puberty will begin at an early age. Neurons of the arcuate nucleus secrete gonadotropin releasing hormone (GnRH) into the blood of the pituitary portal system. These GnRH signals from the hypothalamus induce pulsed secretion of LH (and to a lesser degree, FSH) at roughly 1-2 hour intervals. In the years preceding physical puberty, these gonadotropin pulses occur primarily at night and are of very low amplitude, but as puberty approaches they can be detected during the day. By the end of puberty, there is little day-night difference in the amplitude and frequency of gonadotropin pulses. An array of "autoamplification processes" increase the production of all of the pubertal hormones of the hypothalamus, pituitary, and gonads. Regulation of adrenarche and its relationship to maturation of the hypothalamic-gonadal axis is not fully understood, and some evidence suggests it is a parallel but largely independent process coincident or even preceding central puberty. Rising levels of adrenal androgens (termed adrenarche) can usually be detected between 6 and 11 years of age, even before the increasing gonadotropin pulses of hypothalamic puberty. Adrenal androgens contribute to the development of pubic hair (pubarche), adult body odor, and other androgenic changes in both sexes. The primary clinical significance of the distinction between adrenarche and gonadarche is that pubic hair and body odor changes by themselves do not prove that central puberty is underway.

Hormonal changes of puberty in girls

As the amplitude of LH pulses increases, the theca cells of the ovaries begin to produce testosterone and smaller amounts of progesterone. Much of the testosterone moves into nearby cells called granulosa cells. Smaller increases of FSH induce an increase in the aromatase activity of these granulosa cells, which converts most of the testosterone to estradiol for secretion into the circulation. Rising levels of estradiol produce the characteristic estrogenic body changes of female puberty: growth spurt, acceleration of bone maturation and closure, breast growth, increased fat composition, growth of the uterus, increased thickness of the endometrium and the vaginal mucosa, and widening of the lower pelvis. As the estradiol levels gradually rise and the other autoamplificanton processes occur, a point of maturation is reached when the feedback sensitivity of the hypothalamic "gonadostat" becomes positive. This attainment of positive feedback is the hallmark of female sexual maturity, as it allows the midcycle LH surge necessary for ovulation. Levels of adrenal androgens and testosterone also increase during puberty, producing the typical androgenic changes of female puberty: pubic hair, other androgenic hair as outlined above, body odor, acne. Growth hormone levels rise steadily throughout puberty. IGF1 levels rise and then decline as puberty ends. Growth finishes and adult height is attained as the estradiol levels complete closure of the epiphyses.

Hormonal changes of puberty in boys

Early stages of male hypothalamic maturation seem to be very similar to the early stages of female puberty, though occurring about 1-2 years later. LH stimulates the Leydig cells of the testes to make testosterone and blood levels begin to rise. For much of puberty, nighttime levels of testosterone are higher than daytime. Regularity of frequency and amplitude of gonadotropin pulses seems to be less necessary for progression of male than female puberty. As the testosterone levels slowly rise, most of the effects are mediated through the androgen receptors by way of conversion to dihydrotestosterone in the target tissues (especially of the skin). However, a significant portion of testosterone in adolescent boys is converted to estradiol. Estradiol mediates the growth spurt, bone maturation, and epiphyseal closure in boys just as in girls. Estradiol also induces at least modest development of breast tissue (gynecomastia) in a large proportion of boys.

Historical shift in the onset of puberty

The age at which puberty occurs has dropped significantly since the 1840s. Researchers refer to this drop as the 'secular trend'. From 1840 through 1950, in each decade there was a drop of four months in the average age of menarche among Western European female samples. In Norway, girls born in 1840 had their first menarche at average 17 years. In France in 1840 the average was 15.3 years. In England the 1840 average was 16.5 years for girls and 17.5 for boys. In Japan the decline happened later and was then more rapid: from 1945 to 1975 in Japan there was a drop of 11 months per decade. The most likely cause, as is generally accepted, is the increase of weight gain in the world's youth. Some scientists and researches hypothesize it may be caused by hormones and other additions in processed milk and meats.

Puberty as a problem

- See Precocious puberty
- See Delayed puberty
- See Menarche, gonadarche, pubarche, thelarche, adrenarche.

References

Herman-Giddens ME, Slora EJ, Wasserman RC, et al. Secondary sexual characteristics and menses in young girls seen in office practice: a study from the pediatric research in office settings network. Pediatrics, 1997; 99:501-12. Newer data suggesting we should be using lower age thresholds for evaluation. Plant TM, Lee PA, eds. The Neurobiology of Puberty. Bristol: Society for Endocrinology, 1995. Proceedings of the latest (4th) International Conference on the Control of the Onset of Puberty, containing summaries of current theories of physiological control, as well as GnRH analog treatment. Tanner JM, Davies PS. Clinical longitudinal standards for height and weight velocity for North American children. J Pediatr 1985; 107:317-29. Highly useful growth charts with integrated standards for stages of puberty. Ducros, A. and Pasquet, P. Evolution de l'âge d'apparition des premières règles (ménarche) en France. Biométrie Humaine (1978), 13, 35–43.

External links

- [http://www.nlm.nih.gov/medlineplus/ency/article/001950.htm NIH guide to puberty and adolescence]
- [http://www2.hu-berlin.de/sexology/GESUND/ARCHIV/GUS/INDEXATLAS.HTM Growing Up Sexually: A World Atlas]
- [http://www.youthinformation.com/infomenu.asp?shdID=20 Love and sex section - youthinformation.com]
- [http://www.fpnotebook.com/END34.htm Family Practice Notebook: Sexual Development]
- [http://www.sciencedaily.com/print.php?url=/releases/2005/12/051201022811.htm Research shows how evolution explains age of puberty], ScienceDaily, December 1, 2005.
- Mark Hanson, P. Gluckman. [http://dx.doi.org/10.1016/j.tem.2005.11.006 Evolution, development and timing of puberty], Trends in Endocrinology & Metabolism, January 2006. Category:Human development Category:Sexuality and age ja:思春期

Androgen

Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. This includes the activity of the accessory male sex organs and development of male secondary sex characteristics. Androgens, which were first discovered in 1936, are also called androgenic hormones or testoids. Androgens are also the original anabolic steroids. They are also the precursor of all estrogens, the female sex hormones. The primary and most well-known androgen is testosterone.

Types of androgens

A subset of androgens, adrenal androgens, includes any of the 19-carbon steroids synthesized by the adrenal cortex, an adrenal gland, that function as weak steroids or steroid precursors, including dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), and androstenedione. Besides testosterone, other androgens include:
- Dehydroepiandrosterone (DHEA): a steroid hormone produced from cholesterol in the adrenal cortex, which is the primary precursor of natural estrogens. DHEA is also called dehydroisoandrosterone or dehydroandrosterone.
- Androstenedione (Andro): an androgenic steroid, which is produced by the testes, adrenal cortex, and ovaries. While androstenediones are converted metabolically to testosterone and other androgens, they are also the parent structure of estrone. Use of androstenedione as an athletic or body building supplement has been banned by the International Olympic Committee as well as other sporting organizations.
- Androstanediol: the steroid metabolite that is thought to act as the main regulator of gonadotropin secretion.
- Androsterone: a chemical by-product created during the breakdown of androgens, or derived from progesterone, that also exerts minor masculinising effects, but with one-seventh the intensity of testosterone. It is found in approximately equal amounts in the plasma and urine of both males and females.
- Dihydrotestosterone (DHT): a metabolite of testosterone that is actually a more potent androgen in that it binds more strongly to androgen receptors.

Androgen functions

Development of the male

During mammalian development, the gonads are at first capable of becoming either ovaries or testes. In humans, starting at about week 4 the gonadal rudiments are present within intermediate mesoderm adjacent to the developing kidneys. At about week 6, epithelial sex cords develop within the forming testes and incorporate the germ cells as they migrate into the gonads. In males, certain Y chromosome genes, particularly SRY, control development of the male phenotype, including conversion of the early bipotential gonad into testes. In males, the sex cords fully invade the developing gonads. By week 8 of human fetal development, Leydig cells appear in the differentiating gonads of males. The mesoderm-derived epithelial cells of the sex cords in developing testes become the Sertoli cells which will function to support sperm cell formation. A minor population of non-epithelial cells exists between the tubules, these are the androgen-producing Leydig cells. The Leydig cells can be viewed as producers of androgens that function as paracrine hormones required by the Sertoli cells in order to support sperm production. Soon after they differentiate, Leydig cells begin to produce androgens which are required for masculinization of the developing male fetus (including penis and scrotum formation). Under the influence of androgens, remnants of the mesonephron, the Wolffian ducts, develop into the epididymis, vas deferens and seminal vesicles. This action of androgens is supported by a hormone from Sertoli cells, AMH, which prevents the embryonic Müllerian ducts from developing into fallopian tubes and other female reproductive tract tissues in male embryos. AMH and androgens cooperate to allow for the normal movement of testes into the scrotum. Before the production of the pituitary hormone LH by the embryo starting at about weeks 11-12, human chorionic gonadotrophin (hCG) promotes the differentiation of Leydig cells and their production of androgens. Androgen action in target tissues often involves conversion of testosterone to 5α-dihydrotestosterone (DHT).

Spermatogenesis

During puberty, androgen, LH and FSH production increase and the sex cords hollow out, forming the seminiferous tubules, and the germ cells start to differentiate into sperm. Throughout adulthood, androgens and FSH cooperatively act on Sertoli cells in the testes to support sperm production. Exogenous androgen supplements can be used as a male contraceptive. Elevated androgen levels caused by use of androgen supplements can inhibit production of LH and block production of endogenous androgens by Leydig cells. Without the locally high levels of androgens in testes due to androgen production by Leydig cells, the seminiferous tubules can degenerate resulting in infertility.

Inhibition of fat deposition

Males typically have less adipose tissue than females. Recent results indicate that androgens inhibit the ability of some fat cells to store lipids by blocking a signal transduction pathway that normally supports adipocyte function.

Muscle mass

Males typically have more skeletal muscle mass than females. Androgens promote the enlargement of skeletal muscle cells and probably act in a coordinated manner to enhance muscle function by acting on several cell types in skeletal muscle tissue.

Brain

Circulating levels of androgens can influence human behavior because some neurons are sensitive to steroid hormones. Androgen levels have been implicated in the regulation of human aggression and libido.

Insensitivity to androgen in humans

Reduced ability of a XY karyotype fetus to respond to androgens can result in one of several problems, including infertility and several forms of intersex conditions. See androgen insensitivity syndrome (AIS).

References

# Online textbook: "[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=dbio.TOC&depth=2 Developmental Biology]" 6th ed. By Scott F. Gilbert (2000) published by Sinauer Associates, Inc. of Sunderland (MA). # Online textbook: "[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=endocrin.TOC&depth=1 Endocrinology: An Integrated Approach]" by S. S. Nussey and S. A. Whitehead (2001) published by BIOS Scientific Publishers, Ltd; Oxford, UK. # Full text article available in PDF format: "[http://endo.endojournals.org/cgi/rapidpdf/en.2004-1649v1.pdf Testosterone Inhibits Adipogenic Differentiation in 3T3-L1 Cells: Nuclear Translocation of Androgen Receptor Complex with -Catenin and TCF4 may Bypass Canonical Wnt Signaling to Downregulate Adipogenic Transcription Factors]" by R. Singh, J. N. Artaza, W. E. Taylor, M. Braga, X. Yuan, N. F. Gonzalez-Cadavid and S Bhasin in Endocrinology (2005) # [http://jcem.endojournals.org/cgi/content/full/89/10/5245 Androgen Receptor in Human Skeletal Muscle and Cultured Muscle Satellite Cells: Up-Regulation by Androgen Treatment] by Indrani Sinha-Hikim, Wayne E. Taylor, Nestor F. Gonzalez-Cadavid, Wei Zheng and Shalender Bhasin in The Journal of Clinical Endocrinology & Metabolism (2004 ) volume 89 pages 5245-5255. # Full text article available in PDF format: "[http://www.ncbi.nlm.nih.gov/entrez/utils/lofref.fcgi?PrId=3302&uid=15795710&db=pubmed&url=http://www.medscimonit.com/medscimonit/modules.php?name=GetPDF&pg=2&idm=4259 Testosterone and aggressiveness]" by Marco Giammanco, Garden Tabacchi, Santo Giammanco, Danila Di Majo and Maurizio La Guardia in Endocrinology (2005)

External links

- [http://www.abc.net.au/news/newsitems/s946854.htm News story on the relationship between androgens and heart disease] Category:Androgens ja:アンドロゲン

Testis

The testicles, known medically as testes (singular testis), are the male generative glands in animals. Male mammals have two testicles, which are often contained within an extension of the abdomen called the scrotum. In mammals the testes are located outside of the body as they are suspended by the spermatic cord and within the scrotum. This is due to the fact that spermatogenesis is more efficient at a temperature somewhat less than the core body temperature of 37 degrees Celsius (99 degrees Fahrenheit). The cremasteric muscle is part of the spermatic cord. When this muscle contracts the cord is shortened and the testicle is moved closer up toward the body, which provides slightly more warmth to maintain optimal testicular temperature. When the temperature needs to be lowered, the cremasteric muscle relaxes and the testicle is lowered away from the warm body and are able to cool. This phenomenon is known as the cremasteric reflex. It also occurs in response to stress (the testicles rise up toward the body in an evolutionary effort to protect them in a fight) and they also contract during orgasm. It is normal for one testis to hang lower than the other (usually the left). This is primarily due to differences in the vascular anatomical structure on the right and left sides. It is thought that this is another evolutionary development which protects each testis from bouncing off the other.

Function

Like the ovaries (to which they are homologous), testicles are components of both the reproductive system (being gonads) and the endocrine system (being endocrine glands). The respective functions of the testicles are:
- producing sperm (spermatozoa)
- producing male sex hormones, of which testosterone is the best known Both functions of the testicle, sperm-forming and endocrine, are under control of gonadotropic hormones produced by the anterior pituitary:
- luteinizing hormone (LH)
- follicle-stimulating hormone (FSH)

Structure

Under a tough fibrous shell, the tunica albuginea, the testis contains very fine coiled tubes called the seminiferous tubules. The tubes are lined with a layer of cells that, from puberty into old-age, produce sperm cells. The seminiferous tubules lead to the epididymis, where newly created sperm cells mature, and then into vas deferens (also called the ductus deferens) which opens into the urethra. Upon any sufficient sexual arousal, the sperm cells move through the ejaculatory duct and into the prostatic urethra, where the prostate, through muscular contractions, ejaculates the sperm, mixed with other fluids, out through the penis. (The genital anatomy described here, along with the neuroanatomy and hormonal systems that enable it to perform ejaculation, have as primary evolutionary functions the impregnation of a fertile female of the same species (or a sufficiently close one), via sexual intercourse with her.) sexual intercourse Between the seminiferous tubules are special cells called interstitial cells (Leydig cells) where testosterone and other androgens are formed.

Testicular size

Testicular size in relation to body weight varies widely. In the mammalian kingdom, there is a tendency for testicular size to be larger when the species is more likely to be polygamous than monogamous. Production of testicular output is also larger in the polygamous animal, possibly a spermatogenic competition for survival. In normal adult human males, testicular size ranges from the lower end of around 14 cm³ to the upper end larger than 35 cm³. Measurement in the living adult is done in two basic ways: (1) comparing the testicle with ellipsoids of known sizes (orchidometer), or (2) measuring the length, depth and width with a ruler, a pair of calipers or ultrasound imaging. The volume is then calculated, e.g. using the formula for ellipsoids: π/6 × length × width². Usually right and left testicles have about the same size, but not exactly the same size. To some extent it is possible to change testicular size. Short of direct injury or subjecting them to adverse conditions, e.g. higher temperature than they are normally accustomed to, they can be shrunk by competing against their intrinsic hormonal function through the use of externally administered steroidal hormones. Similarly, stimulation of testicular functions via gonadotrophic-like hormones may enlarge their size.

Health issues

The testicles are well-known to be very sensitive to impact and injury. The most important diseases of testicles are:
- inflammation of the testicles, called orchitis
- testicular cancer and other neoplasms
- accumulation of clear fluid around a testicle, called hydrocele testis
- inflammation of the epididymis, called epididymitis
- spermatic cord torsion also called testicular torsion
- varicocele [http://kidshealth.org/teen/sexual_health/guys/varicocele.html] - swollen vein to the testes, usually affecting the left testicle The removal of one or both testicles is termed
- orchidectomy, in medicine (where orchiectomy and orchectomy are synonymous), and
- castration in general use, especially when done for the benefit of others than the subject, for example, to produce a high-voiced castrato from the castration of a pre-pubescent boy At least for humans, testicular prostheses are available to mimic the appearance and feel of one or both testicles, when absent as from injury or medical treatment.

Adrenarche

Adrenarche refers to a stage of maturation of the cortex of the human adrenal glands. It typically occurs between ages 6 and 10 years and involves both structural and functional changes. Adrenarche is a process related to puberty but distinct from hypothalamic-pituitary-gonadal maturation and function.

Structural and functional changes of adrenarche

Structural changes of adrenarche include increased size and mass of the adrenal cortex, and completion of differentiation into the three zones: zona glomerulosa, zona fasciculata, and zona reticularis. One of the primary functional changes is further differentiation of sex steroid synthesis among the three zones, so that as in adults, the zona glomerlulosa primarily produces mineralocorticoids such as aldosterone, the zona fasciculata primarily produces glucocorticoids such as cortisol, and the zona reticularis primarily produces androgens such as dehydroepiandrosterone, dehydroepiandrosterone sulfate, and androstenedione. The second important functional change is a steady increase over several years in the daily production of adrenal androgens. A characteristic aspect of early adrenarche is an inhibition of 3β-hydroxysteroid dehydrogenase, the enzyme which mediates the hydroxylation of 17-hydroxypregnenolone to 17-hydroxyprogesterone, and DHEA to androstenedione. Blood levels of DHEA, androstenedione, and especially DHEAS can be measured by physicians as markers of adrenal maturation.

Role of adrenarche as part of puberty

An initiator of adrenarche has not yet been identified. Researchers have unsuccessfully tried to identify a new pituitary peptide, to be called "adrenal androgen stimulating hormone". Others have proposed that adrenarchal maturation is a gradual process intrinsic to the adrenal glands that has no distinct trigger. A third avenue of research is pursuing a possible relationship with either fetal or childhood body mass and related signals such as insulin and leptin. Many children born small for gestational age (SGA) because of intrauterine growth retardation (IUGR) have an earlier onset of adrenarche, which raises the possibility that timing of adrenarche may be affected by physiological programming in infancy. Adrenarche also occurs prematurely in many children who are overweight, suggesting a possible relationship with body mass or adiposity signals. The principal physical consequences of adrenarche are androgen effects, especially pubic hair and the change of sweat composition that produces adult body odor. Increased oiliness of the skin and hair and mild acne may occur. In most boys, these changes are indistinguishable from early testicular testosterone effects occurring at the beginning of gonadal puberty. In girls, the adrenal androgens of adrenarche produce most of the early androgenic changes of puberty: pubic hair, body odor, skin oiliness, and acne. In most girls the early androgen effects coincide with, or are a few months behind, the earliest estrogenic effects of gonadal puberty (breast development and growth acceleration). As female puberty progresses, the ovaries and peripheral tissues become more important sources of androgens. Parents and many physicians often infer (incorrectly) the onset of puberty from the first appearance of pubic hair (termed pubarche). However, the independence of adrenarche and gonadal puberty is apparent in children with atypical or abnormal development, when one process may occur without the other. For instance, adrenarche does not occur in many girls with Addison's disease, who will continue to have minimal pubic hair as puberty progresses. Conversely, girls with Turner syndrome will have normal adrenarche and normal pubic hair development, but true gonadal puberty never occurs because their ovaries are defective.

Premature adrenarche

Premature adrenarche is the most common cause of the early appearance of pubic hair (premature pubarche) in childhood. As described above, adrenarche should be distinguished from true central precocious puberty, from congenital adrenal hyperplasia, and from androgen-producing tumors of the adrenals or gonads. Pediatric endocrinologists do this by demonstrating advanced levels of DHEAS and other adrenal androgens, with prepubertal levels of gonadotropins and gonadal sex steroids. As mentioned above, premature adrenarche occurs more often in children with intrauterine growth retardation and in overweight children. Simple premature adrenarche causes no problems for a child and need not be treated but occasionally may precede the condition of excessive androgens in adolescence referred to as polycystic ovary syndrome.

Precocious puberty

Precocious puberty means early puberty. Early pubic hair, breast, or genital development may result from normal but early maturation or from several abnormal conditions. Early puberty which is normal in every way except age is termed idiopathic central precocious puberty. It may be partial or transient. Central puberty can also occur prematurely if the inhibitory system of the brain is damaged, or a hypothalamic hematoma produces pulsatile gonadotropin-releasing hormone (GnRH). Secondary sexual development induced by sex steroids from other abnormal sources (gonadal or adrenal tumors, congenital adrenal hyperplasia, etc.) is referred to as peripheral precocious puberty or precocious pseudopuberty. Early sexual development deserves evaluation because it may : # induce early bone maturation and reduce eventual adult height, # cause significant social problems, or # indicate the presence of a tumor or other serious problem. No single age limit reliably separates normal from abnormal processes, but the following age thresholds for evaluation will minimize the risk of missing a significant problem:
- Pubic hair or genital enlargement in boys with onset before 9 years.
- Breast development in boys before appearance of pubic hair and testicular enlargement.
- Pubic hair before 8 or breast development in girls with onset before 7 years.
- Vaginal bleeding in girls before 10 years. Medical evaluation is sometimes necessary to recognize the few children with serious conditions from the majority who have entered puberty early but are still medically normal. Children (esp. girls) who are obese are more likely to physically mature earlier. Precocious puberty can make a child able to concieve when very young. Both sexs have become parents before age 10.

Androgen

Types of androgens

Androgen functions

Development of the male

Spermatogenesis

Inhibition of fat deposition

Muscle mass

Brain

Insensitivity to androgen in humans

References

External links

- [http://www.abc.net.au/news/newsitems/s946854.htm News story on the relationship between androgens and heart disease] Category:Androgens ja:アンドロゲン

Gonad

The gonad is the organ that makes gametes. Gametes are haploid germ cells. For example, sperm and egg cells are gametes. In vernacular use, gonads is slang for testicles. The usage of such is similar to "balls." As such, in an era where more women are reaching levels of power, one can replace the vernacular saying "He's got balls" to the gender-neutral "They've got gonads". Gonads start developing as a common anlage, and only later are differentiated to male or female sex organs. The SRY gene, located on the Y chromosome and encoding the testis determining factor, decides the direction of this differentiation. Category:Reproductive system

Puberty

Puberty as a physical process

Physical changes of puberty in girls

Breast development

Pubic hair in girls

Vagina, uterus, ovaries

Menstruation and fertility

Pelvic shape, fat distribution, and body composition

Body and facial hair in girls

Height growth in girls

Body odor, skin changes, and acne

Physical changes of puberty in boys

Testicular size, function, and fertility

Genitalia

Pubic hair in boys

Body and facial hair in boys

In the months and years following the appearance of pubic hair, other areas of skin which respond to androgens develop heavier hair in roughly the following sequence: underarm (axillary) hair, perianal hair, upper lip hair, sideburn (preauricular) hair, periareolar hair, and the rest of the beard area. Arm, leg, and back hair become heavier more gradually. There is a large range in amount of body hair among adult men, and significant differences in timing and quantity of hair growth among different ethnic groups.

Voice change

Height growth in boys

Male musculature and body shape

Body odor, skin changes, acne

Breast development in boys: pubertal gynecomastia

Variations of normal puberty

Typical puberty is described above, but many children vary with respect to timing of onset, tempo, steadiness of continuation, and sequence of events.