I told my friend Sue about this site so she is sending me interesting items.  She has an interest in gender things and brains differences.  I was surprised at how young puberty and more active behavior comes, especially in girls!  Oh my.

Neuroendocrinologists Unlock Chemical Trigger to Puberty

May 1, 2005 — Researchers have discovered the precise chemical chain reaction that could be the much-sought-after puberty trigger: The KiSS-1 gene, which produces a protein in the hypothalamus, a part of the brain, which regulates metabolic activity. When the protein connects with a receptor on another gene called GPR54, puberty is believed to begin. This knowledge may guide the development of better drugs for treating hormone disorders related to puberty.

PITTSBURGH--They're politely called "the awkward years," but anybody who can remember going through puberty knows "awkward" is an understatement. Now medical researchers believe they're close to solving the puzzle of puberty.

The awkwardness of growing up is not just a physical phenomenon. It's emotional ... And especially chemical. "Puberty, many people would expect, arises in the gonads and genitals organs. But in fact, puberty arises from the brain," says neuroendocrinologist Tony Plant.

Dr. Plant and a research team from Harvard University and the University of Pittsburgh discovered the precise chemical chain reaction that could be the much sought-after puberty trigger. "The brain sends an endocrine signal to the pituitary gland. This makes protein hormones which reaches the ovaries and testes," Plant says.

It all begins with a kiss -- the KiSS 1 gene, which produces a protein in the hypothalamus. When the protein connects with its receptor, the GPR54 gene, puberty begins.

Dr. Plant says this is the first real handle we've had on the issue of the trigger. With wide variation, that trigger is pulled sometime between ages 10 and 16. But early or late puberty can pose developmental problems, like behavior problems and low self-esteem. Pediatricians have to treat these children with either precocious or delayed puberty.

Puberty is the developmental stage where a child starts to become sexually mature. It can occur between ages 8 and 11 for girls, and 9 to 12 for boys.

As a child nears maturity, the brain -- specifically the parts known as the hypothalamus and the pituitary gland -- releases chemicals called hormones. The hormones regulate the reproductive organs of both males and females. Girls produce estrogen and progesterone, while boys produce testosterone. Growth hormones also begin to work, causing the body to become larger, sometimes very quickly. The body also makes follicle stimulating hormones, leading to hair growth. All these extra hormones give rise to dramatic changes in the body.

The first sign of puberty in girls is breast development. Then hair starts growing in the pubic area and armpits, followed by acne around age 13. Menstruation is typically the last stage to occur.

In boys, the larynx lengthens and the voice "breaks" and then deepens. Also, there is growth in the testicles and penis, followed by hair growth in the pubic region and armpits. Acne and facial hair are the last developments. Both girls and boys may also experience strong emotions or mood changes.