| Summary: | We studied the relationships between polychlorinated biphenyls (PCBs) and thyroid hormones (THs) and retinol within two groups of female polar bears (Ursus maritimus), females with cubs of the year (FWCOY) and females without cubs of the year (FWOCOY), and within a group of males. Concentrations of five of the six quantified PCB congeners, i.e., PCB-99, PCB-153, PCB-156, PCB-180, PCB-194 (ΣPCB 5), correlated with each other, whereas the concentrations of PCB-118 did not correlate with the other congeners. ΣPCB 5 and PCB-118 did not differ between the three different groups of polar bears, and the plasma levels ranged from 16.7 to 203.2 ng/g wet weight (ww) for ΣPCB 5 and from 0.09 to 0.93 ng/g ww for PCB-118. PCBs did not affect the retinol status in any of the three groups. In FWCOY, we found negative correlations between ΣPCB 5 and the three TH variables free thyroxin (FT 4) (r 2 = 0.35), free triiodothyronine (FT 3) (r 2 =0.30), and the total T 4:total T 3 ratio (TT 4:TT 3) (r 2 = 0.92). In FWOCOY, ΣPCB 5 was negatively correlated to TT 4 (r 2 = 0.14) and positively correlated to TT 3:FT 3 (r 2 = 0.31), whereas PCB-118 was positively correlated to FT 3 (r 2 = 0.21) and negatively correlated to TT 3:FT 3 (r 2 =0.26). In males, ΣPCB 5 was negatively correlated to FT 3 (r 2 = 0.56) and positively correlated to FT 4:FT 3 (r 2 = 0.78), whereas PCB-118 was negatively correlated to FT 4:FT 3
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