Bone-related effects of contaminants in seals may be associated with vitamin D and thyroid hormones

• Published in: Environmental toxicology and chemistry 2008-04, Vol.27 (4), p.873-880
• Main Authors: Routti, Heli, Nyman, Madeleine, Jenssen, Bjørn Munro, Bäckman, Christina, Koistinen, Jaana, Gabrielsen, Geir Wing
• Format: Article
• Language: English
• Subjects: Animals; Aquatic mammals; Baltic Sea; Bioaccumulation; Bone and Bones - drug effects; Contaminants; Correlation analysis; Environmental contaminants; Halichoerus grypus; Hormones; Lesions; Liver - anatomy & histology; Marine; PCB; Phoca hispida botnica; Pollution load; Polychlorinated biphenyls; Seal; Seals; Seals, Earless - metabolism; Studies; Thyroid; Thyroid gland; Thyroid Gland - drug effects; Thyroid hormone; Thyroid Hormones - blood; Vitamin D; Vitamin D - analysis; Vitamin D - metabolism; Water Pollutants, Chemical - toxicity
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1897/07-139.1

The high levels of polychlorinated biphenyls (PCBs) and DDT in gray seal (Halichoerus grypus) and ringed seal (Phoca hispida botnica) in the Baltic Sea have been associated with pathological disruptions, including bone lesions and reproductive failures. The underlying environmental and toxicological mechanisms leading to these pathological changes are not yet fully understood. The present study investigated the relationship between the individual contaminant load and bone‐ and thyroid‐related effects in adult gray seals (n = 30) and ringed seals (n = 46) in the highly contaminated Baltic Sea and in reference areas (Sable Island, Canada, and Svalbard, Norway). In the gray seals, multivariate and correlation analyses revealed a clear relationship between circulating 1,25‐dihydroxyvitamin D3 (1,25(OH)2D), calcium, phosphate, and thyroid hormone (TH) levels and hepatic PCB and DDT load, which suggests contaminant‐mediated disruption of the bone and thyroid homeostasis. Contaminants may depress 1,25(OH)2D levels or lead to hyperthyroidism, which may cause bone resorption. In the ringed seals, associations between circulating 1,25(OH)2D, THs, and hepatic contaminants were less prominent. These results suggest that bone lesions observed in the Baltic gray seals may be associated with contaminant‐mediated vitamin D and thyroid disruption.