Environmental Effects on Hormone Activity

Some compounds present in the environment, both from natural and man-made sources, can disrupt the delicate hormone balance necessary for reproduction in several species possibly including horses, according to Cynthia Corbitt Gulledge, PhD, of the University of Louisville’s biology department. Gulledge presented “Hormones and Anti-Hormones in the Environment: Relevance for Equine Reproduction” at the Hagyard-Davidson-McGee Bluegrass Equine Reproduction Symposium Oct. 23-26 in Lexington, Ky.

“Chemical confusion can result when environmental chemicals trick the body into thinking that they’re the natural ones,” she stated. Another problem is when environmental chemicals block the action of an animal’s hormones. She cited instances of infertility, subfertility, feminization of males, and altered puberty due to environmental chemicals/hormones that had been documented in other species. Her suggestion was that although this cause of reproductive dysfunction had not been studied in horses, it should be considered in cases of reproductive abnormalities with no apparent cause.

Sources of environmental hormones/anti-hormones include some plants (many plants contain phytoestrogens, or plant-made estrogens), agricultural runoff (crop pesticides, and pharmaceuticals from feedlot runoff), industrial waste, treated sewage, personal care products (some sunscreens and hair care products), lawn care products, and insecticides.

Gulledge explained that the effects of these chemicals can depend on the age of the animal when exposed to them (fetal exposure can have permanent developmental effects while adult exposure might result in much smaller effects) and the specific roles of hormones in each species (which vary in their normal activity by species and thus their susceptibility to outside hormonal influence). For further information, she recommended the Center for Bioenvironmental Research’s web site at www.som.tulane.edu/ecme/eehome/.

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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