| Effects of Organochlorine Contaminants on Thyroid Hormone Levels in Arctic Breeding Glaucous Gulls, Larus hyperboreus Jonathan Verreault,1,2 Janneche Utne Skaare,3,4 Bjørn Munro Jenssen,5 and Geir Wing Gabrielsen1 1Norwegian Polar Institute, Tromsø, Norway; 2Department of Ecology and Zoology, University of Tromsø, Tromsø, Norway; 3Norwegian School of Veterinary Science, Oslo, Norway; 4National Veterinary Institute, Oslo, Norway; 5Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway Abstract
Studies on glaucous gulls (Larus hyperboreus) breeding in the Barents Sea have reported that high blood levels of halogenated organic contaminants in this species might cause reproductive, behavioral, and developmental stress. However, potential endocrine system modulation caused by contaminant exposure has yet not been reported in this Arctic apical predator. In this present study we aimed to investigate whether the current levels of a selection of organochlorines (OCs) were associated with altered circulating levels of thyroid hormones (THs) in free-ranging adult glaucous gulls breeding at Bear Island in the Barents Sea. Blood concentrations of 14 polychlorinated biphenyls, hexachlorobenzene (HCB) , oxychlordane, and p,p´-dichlorodiphenyldichloroethylene (p,p´-DDE) were quantified, in addition to free and total thyroxine (T4) and triiodothyronine (T3) , in plasma of 66 glaucous gulls in the spring of 2001. Negative correlations were found between plasma levels of T4 and T4:T3 ratio, and blood levels of OCs in male glaucous gulls. Despite their relatively low contribution to the total OC fraction, HCB and oxychlordane were the most prominent compounds in terms of their negative effect on the variation of the T4:T3 ratio. Moreover, lower T4 levels and T4:T3 ratios were measured in glaucous gulls breeding in a colony exposed to high levels of OCs, compared with a less exposed colony. Levels of T3 were elevated in the high-OC-exposed colony. This may indicate that the glaucous gull is susceptible to changes to TH homeostasis mediated by exposure to halogenated organic contaminants. Key words: Arctic, contaminant, endocrine disruption, glaucous gull, organochlorine, T3, T4, thyroid hormone. Environ Health Perspect 112:532-537 (2004) . doi:10.1289/ehp.6756 available via http://dx.doi.org/ [Online 9 December 2003]
Address correspondence to J. Verreault, Norwegian Polar Institute, The Polar Environmental Centre, NO-9296 Tromsø, Norway. Telephone: 47-77-75-05-42. Fax: 47-77-75-05-01. E-mail: jonathan@npolar.no K Borgå, J.O. Bustnes, G.A. Fox, and two anonymous reviewers provided valuable comments on the manuscript. This project received financial support from the Norwegian Polar Institute's Ecotoxicology Programme. The authors declare they have no competing financial interests. Received 23 September 2003 ; accepted 9 December 2003.
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