Environmental health impacts of equine estrogens derived from hormone replacement therapy.

The research explores the potential environmental risks posed by equine estrogens (common components in hormone replacement therapy for menopausal women), specifically their effects on aquatic wildlife. The study discovered that these hormones could indeed enter the environment, bioaccumulate in aquatic organisms, and induce estrogen-related phenotypes and biological effects.

Methodology

• The team investigated the presence of six equine estrogens in influents and effluents from four U.K. sewage treatment works (STWs), as well as in bile from fish exposed to these effluents. This was done via a screening method.
• In vitro estrogen receptor (ER) activation assays were conducted on humans and fish to compare and contrast the effect of these hormones on different species.
• Next, the researchers exposed fish to these equine estrogens in vivo to study their bioaccumulation, ER gene expression, and estrogenic responses, which include hepatic growth and vitellogenin production.

Results and Findings

• They detected the presence of equine estrogen equilenin (Eqn), and its metabolite 17beta-dihydroequilenin (17beta-Eqn) in all the influent samples and 83% of STW effluent samples. These samples contained low concentrations of these hormones (ranging between 0.07-2.6 ng/L). Additionally, it was observed that these estrogens were absorbed by fish exposed to the STW effluents.
• In vitro ER activation assays showed that these hormones could bind to and activate both human and fish ERs, with different levels of potency.
• In vivo exposure to Eqn and 17beta-Eqn for 21 days resulted in estrogenic responses in fish at concentrations as low as 0.6-4.2 ng/L. These responses included hepatic growth and vitellogenin production. Additionally, genes expression of hepatic ERalpha and ERbeta1 was induced, indicating an ER-mediated mechanism of action.

Conclusion

• The findings suggest that, due to the application of equine estrogens in hormone replacement therapy, these hormones are finding their way into the aquatic environment and are potentially causing feminization effects in exposed aquatic life.
• This work underscores the need for considering environmental risks associated with pharmaceuticals like hormone replacement therapy, informing risk-benefit evaluations more above and beyond their effect on human health.