الفهرس 
Physiology of pubertyOnly 14 pages are availabe for public view
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Abstract
Puberty is the process of physical changes through which a child’s body matures into an adult body capable of sexual reproduction. It is caused by reactivation of the hypothalamic-pituitary-gonadal (HPG) axis resulting in gonadal estradiol and testosterone secretion. The HPG axis is transiently activated during early infancy followed by a long period of relative quiescence. The process of puberty lasts for 3–5 years.
In response to the hormonal signals, the gonads produce hormones that stimulate the growth of the brain, bones, muscle, blood, skin, hair, breasts and sex organs. Physical growth (height and weight) accelerates in the first half of puberty and is completed when an adult body has been developed.
Puberty usually begins between 8 and 13 years of age in girls and 9 and 14 years of age in boys. On average, girls begin puberty at ages 10–11; boys at ages 11–12 (puberty in boys typically begins approximately a year later than girls). Girls usually complete puberty by ages 15–17, while boys usually complete puberty by ages 16–17 years.
Some variability occurs between individuals with regard to the timing and sequence of pubertal maturation. However, most of boys and girls follow a predictable course through pubertal maturation. The timing and duration of pubertal events could vary among different ethnic groups, but nevertheless, the sequence of events underlying pubertal development is similar in boys and girls worldwide.
Endocrine-disrupting chemicals (EDCs) have been implicated as being environmental factors affecting pubertal onset. Endocrine disrupters can cause pubertal disorders by several mechanisms. They can act as hormone agonists or antagonists or both depending on the dose and background hormone levels, i.e.,