Several Synthetic Progestins with Different Potencies Adversely Affect Reproduction of Fish

Synthetic progestins are widely used as a component in both contraceptives and in hormone replacement therapy (HRT), both on their own and in combination with EE2. Their presence in the environment is now established in wastewater effluent and river water and this has led to concerns regarding their potential effects on aquatic organisms living in these waters. We carried out in vivo experiments to determine the potencies of four different synthetic progestins on the reproductive capabilities of the fathead minnow (Pimephales promelas). We then performed a series of in vitro assays to try and determine the reason for the effects seen in the in vivo experiments. In the first experiment, fathead minnow exposed to a single concentration of 100 ng/L of either Levonorgestrel or Gestodene stopped spawning almost completely. The same nominal concentration of Desogestrel and Drospirenone did not affect reproduction (21 d NOECs of 100 ng/L). The second experiment investigated two progestins of different potency: G...