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Link found between cattle growth hormone and reproductive malformations in minnows

2 July 2003

Research conducted by the U.S. Environmental Protection Agency (EPA) has found a link between a widely used cattle growth hormone, trenbolone acetate, and reproductive abnormalities in fathead minnows.

The team of researchers, led by Dr. Gerald T. Ankley, a research toxicologist for the EPA, Mid-Continent Ecology Division, in Duluth, Minn., found that trenbolone decreases the reproductive capacity of the fish at very low concentrations in the water. Trenbolone also disrupts endocrine function in the fish and causes the female fathead minnows to develop male secondary sex characteristics, parallel to the masculinization seen in women exposed to anabolic androgen steroids (AAS).

Ankley and his team say that excretions from livestock treated with trenbolone acetate contain the relatively potent androgen receptor agonist 17-ß-trenbolone that, based on other studies, appears to be persistent in the environment. This suggests that animals, particularly those in aquatic environments, may be unintentionally exposed to trenbolone via runoff originating from feedlots.

The research is discussed in the article, "Effects of the Androgenic Growth Promoter 17-ß-Trenbolone on Fecundity and Reproductive Endocrinology of the Fathead Minnow," printed in the June 2003 issue of Environmental Toxicology and Chemistry, a monthly journal published by the Society of Environmental Toxicology and Chemistry (SETAC).

Trenbolone acetate is an AAS that mimics the action of testosterone by enhancing growth through the addition of lean muscle mass, a highly-desirable attribute in livestock. The hormone is administered to livestock via slow-release implants where, upon entry into the bloodstream, it is quickly converted to 17-ß-trenbolone.

Use of these hormones has been approved because only minute concentrations are found in the meat from treated livestock. However, little research has been conducted addressing the potential effects of the hormones after being excreted into the environment.

"This is the first published study demonstrating evidence of reproductive toxicity and endocrine impacts of trenbolone in fish exposed to relatively small concentrations of the chemical via the water," Ankley said.

The use of trenbolone acetate presents a significant economic benefit to livestock producers and consumers. Treated cattle increase mass but consume less feed than untreated cattle. Therefore, trenbolone allows livestock producers to raise lean cattle at a lower cost and consumers to pay lower prices for lean meat.

Despite the benefits of its use, further studies are warranted to assess the potential ecological threat of trenbolone acetate and its continued use as a cattle growth promoter.

Contact:
April Phillips
Society of Environmental Toxicology and Chemistry
Public Relations
850 469 1500 x 28
aprilp@setac.org