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'Male' Hormone Tied to Early Puberty in Girls


The hormone estrogen is most abundant in women and associated with the development of 'female' characteristics, like breasts. Testosterone, on the other hand, is seen in its highest proportions in men and is associated with 'male' characteristics, like muscle development and body hair. Both hormones, however, are found to some degree in both men and women.

Until recently, it was assumed that estrogen is a key player in puberty in young girls, but this new research points the finger at testosterone. Does that mean that testosterone levels affect cancer risk?

To help unravel the association between testosterone and puberty, Fred F. Kadlubar, MD, director of the division of molecular epidemiology at the FDA National Center for Toxicological Research in Jefferson, Ark., and colleagues studied nearly 200 white, black, and Hispanic girls aged 9-10. The researchers noted when the girls started puberty and recorded information about their diet, weight, and environment. Genetic testing also was used to identify any genetic differences among the girls that would explain how their hormones would affect their health.

The researchers found that girls whose genetic makeup caused them to produce higher levels of a liver enzyme that breaks down testosterone, called CYP3A4, tended to start puberty earlier. These findings suggest that girls with relatively low levels of testosterone might experience early puberty and hence a higher risk of breast cancer.

"Because the early onset of puberty is a risk factor for breast cancer, it won't be surprising if studies of this genetic variance and breast cancer also find it to be a risk factor," Kadlubar said.

Next, Kadlubar and his team will look at how this same genetic variation affects the onset of puberty in young boys. He expects to find an opposite relationship. That is, boys with the highest levels of testosterone in their bodies should start puberty soonest.

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