Exposure to mixtures of organohalogen contaminants and associative interactions with thyroid hormones in East Greenland polar bears (Ursus maritimus)

Concentrations of vitamin A, E, thyroid and testosterone hormones in blood plasma and tissues from emaciated adult male Arctic foxes (Vulpes lagopus) dietary exposed to persistent organic pollutants (POPs)

“…The apparent small effects on circulating concentrations of thyroid hormones in the present POPs exposed adult male foxes were in contrast to reports of lowered levels of FT3, TT3, FT4 and TT4 in adult female Greenland dogs that also were exposed to dietary consumption of POPs (Kirkegaard et al, 2011), and the associations between POPs and thyroid hormones reported in several other free-living Arctic mammals (Braathen et al, 2004;Gabrielsen et al, 2015;Knott et al, 2011;Villanger et al, 2011aVillanger et al, , 2011b. In some of these studies, thyroid hormone levels in females appear to be more affected by POPs.…”

“…polar bears, seal spp. and beluga whales (Delphinapterus leucas) Gabrielsen et al, 2015;Letcher et al, 2010;Simon et al, 2013;Sonne, 2010;Villanger et al, 2011aVillanger et al, , 2011b. POP exposure is also known to induce oxidative stress through the production of peroxides and free radicals that may damage components of the cell, including proteins, lipids, and DNA (Palace et al, 1996b;Twaroski et al, 2001aTwaroski et al, , 2001b.…”

Potentiation of ecological factors on the disruption of thyroid hormones by organo-halogenated contaminants in female polar bears (Ursus maritimus) from the Barents Sea

“…Several OHCs are known to have endocrine disruptive properties (Gore et al, 2015) and thyroid hormones (THs) have been widely used as biomarkers of pollutant exposure in marine mammals (Jenssen, 2006;Routti et al, 2008) and polar bears in particular (Braathen et al, 2004;Knott et al, 2011;Villanger et al, 2011a;Gabrielsen et al, 2015). THs have ubiquitous roles, controlling thermoregulation, metabolism and reproduction (McNabb, 1995).…”

Barents Sea polar bears (Ursus maritimus): population biology and anthropogenic threats

“…In Svalbard polar bears, a possible immunotoxic effect and negative association between organochlorines and retinol and thyroid hormones have been reported . Studies indicate that organic pollutants have a negative effect on immune response and metabolism in polar bears (Lie et al , 2005Braathen et al 2004;Villanger et al 2011). Contaminants in polar bears have been studied in most parts of the species range Verreault et al 2005;Muir et al 2006;Mckinney et al 2011).…”

“…In 1975, concern was raised for the first time regarding high levels of pollutants found in polar bear tissues (Bowes & Jonkel 1975). Contaminants continue to be a significant threat to polar bear health Obbard et al 2010;Sonne 2010;Dietz, Basu et al 2013;) and recent findings regarding effects on immune responses and metabolism highlight the complexity of this issue (Braathen et al 2004;Lie et al 2004Lie et al , 2005Villanger et al 2011). Today, polar bears are included in several monitoring programmes because they are seen as indicators of the environmental condition of the Arctic and because of international obligations: MOSJ (Sander et al 2005), Arctic Monitoring and Assessment Program (Nilsson & Huntington 2009) and Conservation of Arctic Flora and Fauna (Vongraven & Peacock 2011;Vongraven et al 2012).…”