| Summary: | High concentrations of polychlorinated biphenyls (PCBs) in polar bears from Svalbard have increased concern for that population’s reproductive health. We examined whether there were associations between the plasma concentrations of PCBs and reproductive hormones [progesterone (P 4) and 17β-estradiol (E 2)] in free-living female polar bears from Svalbard. Concentrations of P 4 depended on reproductive status, and concentrations were lowest in females with offspring—females with cubs and females with yearlings. In these females, the P 4 concentrations were positively correlated with plasma ΣPCBs (sum of all analyzed polychlorinated biphenyl congeners) concentrations. The ΣPCBs concentrations explained 27 % of the variation in the P 4 concentrations. There were no correlations between ΣPCBs and E 2 and cortisol in any of the groups of polar bears, or between ΣPCBs and P 4 in single polar bears. Although the ΣPCBs–P 4 relationship in female polar bears with offspring is not evidence per se of a direct cause–effect association, the results indicate that PCBs may affect levels of P 4 in polar bear females. There is a clear need to further assess the hormone balance and population health of polar bears at Svalbard. Key words:
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