Perspectives Online

Neuroscientist gets NIEHS grant to study causes of early puberty in girls

Heather Patisaul

An N.C. State University neuroscientist has received $1.9 million over five years from the National Institute of Environmental Health Sciences (NIEHS) to study the relationship between exposure to certain chemical compounds and the onset of early puberty in females.

Dr. Heather Patisaul, assistant professor of zoology in the university’s College of Agriculture and Life Sciences, received one of NIEHS’ 2007 Outstanding New Environmental Scientist awards. Her research will focus on determining how early puberty occurs after exposure to either a synthetic compound called Bisphenol-A, a plastics component commonly found in canned food lining and plastic beverage bottles, or naturally occurring compounds found in soybeans.

“More than 50 percent of girls in western countries are showing significant signs of puberty before the fifth grade,” Patisaul said. “Some are showing signs in first and second grade. And it’s even earlier in African-American populations than in white populations.” The coupling of early puberty with societal shifts in marriage and pregnancy — women are waiting longer to have children, so Patisaul says it’s more and more common for 20 years to elapse between first ovulation and first pregnancy — can result in serious consequences for women’s reproductive health.

There are a number of endocrine active compounds — or those that act on the endocrine system — in the environment, Patisaul says. Some occur naturally, like those produced by soybean plants, while others are synthetic compounds found in pesticides or plastics, for example. Patisaul’s interests include those that mimic estrogen, the primary female sex hormone.

In normal female development, surges of estrogen give the green light to a set of neurons in the brain, gonadotropin-releasing hormones, to stimulate ovulation.

“The way this system is organized matters greatly to the timing of puberty and fertility,” Patisaul says.

Endocrine active compounds, however, can throw off this delicately balanced system, Patisaul says. They can interact with estrogen receptors — cell proteins that sense the presence of estrogens and then work to regulate gene expression — and either speed up or block certain effects of estrogen.

Patisaul’s NIEHS study will expose rats and mice to soy phytoestrogens and Bisphenol-A to attempt to discern if and how they react with two different estrogen receptors — called ERa and ERß.

“Soy phytoestrogen and Bisphenol-A are estrogen mimics, and they can either act like estrogen or block the effects of estrogen,” Patisaul says. “Effects are often region- and tissue-specific, so these estrogen mimics may block effects of estrogen in the brain and enhance effects of estrogen in ovaries, for example. We’ll mix and match combinations of compounds with the two estrogen receptors and see if these endocrine active compounds really could be one of the factors changing the timing of puberty in females.”

—NCSU News Services