Associations between complex OHC mixtures and thyroid and cortisol hormone levels in East Greenland polar bears.

abstract The multivariate relationship between hair cortisol, whole blood thyroid hormones, and the complexmixtures of organohalogen contaminant (OHC) levels measured in subcutaneous adipose of 23 EastGreenland polar bears (eight males and 15 females, all sampled between the years 1999 and 2001) wasanalyzed using projection to latent structure (PLS) regression modeling. In the resulting PLS model,most important variables with a negative influence on cortisol levels were particularly BDE-99, but alsoCB-180, -201, BDE-153, and CB-170/190. The most important variables with a positive influence oncortisol were CB-66/95, a -HCH, TT3, as well as heptachlor epoxide, dieldrin, BDE-47, p,p 0 -DDD.Although statistical modeling does not necessarily fully explain biological cause–effect relationships,relationships indicate that (1) the hypothalamic–pituitary–adrenal (HPA) axis in East Greenland polarbears is likely to be affected by OHC-contaminants and (2) the association between OHCs and cortisolmay be linked with the hypothalamus–pituitary–thyroid (HPT) axis.& 2012 Elsevier Inc. All rights reserved.