Endocrine-disrupting effects of cattle feedlot effluent on an aquatic sentinel species, the fathead minnow

Edward F. Orlando, Ana S. Kolok, Gerry A. Binzcik, Jennifer L. Gates, Megan K. Horton, Christy S. Lambright, L. Earl Gray, Ana M. Soto, Louis J. Guillette

Research output: Contribution to journalArticlepeer-review

312 Scopus citations


Over the last decade, research has examined the endocrine-disrupting action of various environmental pollutants, including hormones, pharmaceuticals and surfactants, in sewage treatment plant effluent. Responding to the growth of concentrated animals feeding operations, (CAFOs) and the pollutants present in their wastewater (e.g., nutrients, pharmaceuticals, and hormones), the U.S. Environmental Protection Agency developed a new rule that tightens the regulation of CAFOs. In this study, we collected wild fathead minnows (Pimephales promelas) exposed to feedlot effluent (FLE) and observed significant alterations in their reproductive biology. Male fish were demasculinized (having lower testicular testosterone synthesis, altered head morphometrics, and smaller testis size). Defeminization of females, as evidenced by a decreased estrogen:androgen ratio of in vitro steroid hormone synthesis, was also documented. We did not observe characteristics in either male or female fish indicative of exposure to environmental estrogens. Using cells transfected with the human androgen receptor, we detected potent androgenic responses from the FLE. Taken together, our morphologic, endocrinologic, and in vitro gene activation assay data suggest two hypotheses: a) there are potent androgenic substance(s) in the FLE, and/or b) there is a complex mixture of androgenic and estrogenic substances that alter the hypothalamic-pituitary-gonadal axis, inhibiting the release of gonadotropin-releasing hormone or gonadotropins. This is the first study demonstrating that the endocrine and reproductive systems of wild fish can be adversely affected by FLE. Future studies are needed to further investigate the effects of agricultural runoff and to identify the biogically active agents, whether natural or pharmaceutical in origin.

Original languageEnglish
Pages (from-to)353-358
Number of pages6
JournalEnvironmental Health Perspectives
Issue number3
StatePublished - Mar 2004
Externally publishedYes


  • Anabolic steroid hormones
  • Aquatic ecosystem health
  • Concentrated animal feeding operation (CAFO)
  • Environmental androgens and estrogens
  • Gene expression
  • HPG axis
  • Hypothalmic-pituitary-gonadal axis
  • Pharmaceuticals and personal care products (PPCPs)
  • Pimephales-promelas


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