PCBs and reproductive hormones in female polar bears

Summary

High concentrations of PCBs in polar bears from Svalbard have resulted in growing concerns for the population�s reproductive health. We examined if there were associations between the plasma concentrations of PCBs and reproductive hormones (progesterone [P4] and 17β- estradiol [E2]) in free-living female polar bears from Svalbard. Concentrations of P4 were dependent on reproductive status, and concentrations were lowest in females with offspring i.e., females with cubs and females with yearlings. In these females the P4 concentrations were positively correlated with plasma ΣPCBs concentrations. The ΣPCBs concentrations explained 27% of the variation in the P4 concentrations. There were no correlation between ΣPCBs and E2 in any of the groups of polar bears, or between ΣPCBs and P4 in single polar bears. Although the ΣPCBs - P4 relationship in female polar bears with offspring is not evidence per se of a direct cause-effect association, the results may represent an indication that PCBs may affect levels of progesterone in polar bear females. There is a clear need to further assess the hormone balance and population health of polar bears at Svalbard.