Monday, August 9, 2010

Puberty: How Early is "Too Early?"

A study published today in the journal Pediatrics indicates that among girls in the United States, the onset of puberty is earlier than it has ever been.

Lead investigator Dr. Frank Biro of Cincinnati Children's Hospital examined approximately 1,200 girls aged 7 and 8 years and determined that among 7-year olds, 10 percent of Caucasian girls and 23 percent of African-American girls had started developing breasts, the earliest sign of pubertal development in girls. Among the 8-year olds, 18 percent of Caucasian girls and 43 percent of African-American girls had entered puberty.

This is a stark contrast from a similar study in 1997, when among 7-year olds, 5 percent of Caucasian and 15 percent of African-American girls had started puberty. In the 1997 study, among 8-year olds, 11 percent of Caucasian girls and 43 percent of African-American girls had started puberty.

But why?

Anecdotally, pediatric endocrinologists have noted the exact same findings over the past 20 years as published today, so it doesn't come as a complete shock to the medical community. Theories include: a change in nutritional intake (more heavily dependent on proteins and carbohydrates and lower in fiber than before); contamination of the water supply and meats with steroids and other products given to livestock or found in plastics, like BPA; and the significant increase in the obese population among children.

I personally believe this latter problem is at the heart of the matter.

The hormone leptin is a key player in telling the brain "enough is enough" when it comes to eating. After a filling meal, the amount of leptin in the bloodstream increases, and when leptin reaches the hunger centers in the hypothalamus (an area in the central brain), the body gets the signal that it is full.

Leptin also has been found to play a key role in instructing the hypothalamus and pituitary glands to release the hormones GnRH (in the hypothalamus) and subsequently FSH and LH (in the pituitary gland), the latter two of which are in charge of starting puberty.

In children who are overweight or obese, there is a higher amount of leptin in the bloodstream due to the fact that the child's nutritional intake -- especially compared to lean peers -- is in excess. The body, by releasing more leptin, is trying to tell the child to "stop eating." The side effect of this is that even at a young age, the excess leptin tells the brain to release the hormones of puberty, which gets the process started earlier than one would expect.

In other words, obesity leads to increased leptin. Increased leptin tells the hormones of puberty to kick in. And if the child is overweight or obese from a young age, this all starts earlier than ever before.

Yet another reason to continue to work hard on curbing the obesity epidemic.

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