Discovery May Help Doctors Treat Infertility

A new study shows that fertility drugs may be ineffective for women who lack a gene called the estrogen receptor beta, suggesting that women who lack this receptor may need alternative infertility treatments. This discovery was reported in the August 2005 issue of Endocrinology.

The estrogen receptor beta is one of two estrogen proteins that mediate the effects of estrogen hormones and are present throughout female reproductive tissue. In mice that were genetically engineered to lack the estrogen receptor beta, fertility drugs did not improve ovulation rates, indicating that this receptor plays a critical role in ovulation.

"What we found is that the beta estrogen receptor plays a role in moving the egg outside the ovary so it can be fertilized,” said Kenneth Korach, Ph.D., laboratory chief at the U.S. National Institute of Environmental Health Sciences (NIEHS, Bethesda, MD, USA), where the research took place. "We never knew before what function this receptor played in reproduction.”

If the results from this animal study are found to be applicable to humans, a simple blood test will be able to provide enough information to determine if a genetic mutation may be altering the function of the estrogen receptor beta. Coupled with other information from medical tests, this test will also help diagnose infertility and help determine treatment options.

It was generally thought that there was only one receptor, the alpha receptor, that responded to estrogen. It was not until 1996 that the estrogen receptor beta was discovered. According to the current study, the beta receptor plays a more significant role in ovarian function than the alpha receptor.

The beta receptor is also known to respond to environmental and dietary chemicals that can mimic the effects of estrogen and stimulate the body's natural hormones. One example of this is genistein, a component of soy products. The new findings suggest that such environmental exposures could interact with estrogen receptor beta and possibly alter ovarian function. An earlier NIEHS study used an in vitro approach to reveal the role that estrogen receptors play in ovulation.

"The tools and animal models necessary to do these types of studies have only recently become available, but are already helping us to better understand the role of estrogen in the ovary,” stated lead author John Couse, Ph.D.




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National Institute of Environmental Health Sciences