Internal exposure of whitefish (Coregonus lavaretus) to estrogens

Gonad malformations have been found in fish all over the world. Particularly in Lake Thun (Switzerland) a high prevalence of gonad deformations in whitefish has been observed. Very often, a link between exposure to endocrine disrupting compounds and altered gonad morphology exists. Hence, we analyzed the estrogenic burden in bile and muscle from whitefish (coregonids) from Lake Thun and linked it to observed gonad malformations. Estrogenicity in bile, measured with the yeast estrogen screen (YES) was exclusively caused by the natural steroids estrone and 17beta-estradiol. Estrogenicity determined in muscle tissue using YES was similar in cases and controls, and between the sexes. Furthermore, endocrine active compounds in the lake water were investigated using passive sampling devices to monitor tributaries and the main outflow of Lake Thun. Here, we found accumulated estrogenicity. With target chemical analysis small amounts of estrone and bisphenol A were determined. We conclude, that the whitefish from Lake Thun are not suffering from (xeno)estrogens. The present study contributed substantially to the search for the cause for gonad malformations in Lake Thun whitefish, even though the cause of the malformations remains yet to be discovered.