Gender benders at the beach: endocrine disruption in marine and estuarine organisms

Several consensus definitions of the term endocrine disruptor have appeared recently, but all definitions include the important, though frequently implicit, stipulation that the animal is not distressed or in obvious discomfort. Instead, a superficially healthy animal is experiencing alterations in hormone synthesis, transport, receptor interaction, metabolism, excretion, or feedback regulation. In addition, hormone disruption may occur during sex differentiation, and its effects may not be manifested until after sexual maturation. Many cases of chemically induced reproductive impairment have been reported for both freshwater and marine species. However, reproductive impairment may not necessarily result from hormone disruption and should be considered suggestive, but not conclusive, evidence of endocrine disruption. A suite of in vivo and in vitro assays will more adequately assess whether a compound is truly endocrine disrupting. This review will cover basic endocrinology of marine and estuarine invertebrates and vertebrates, methods for detecting endocrine disruption, and examples of endocrine disruption in various species.