Thyroid hormone status in gray seal (Halichoerus grypus) pups from the baltic sea and the atlantic ocean in relation to organochlorine pollutants

Abstract

Marine apex predators, such as the gray seal (Halichoerus grypus), are exposed to high concentrations of organochlorine (OC) compounds via biomagnification in the food web. These lipophilic pollutants are transferred from the female to her offspring during lactation, and there is particular concern for endocrine disruption in the offspring. Herein we examined associations between the blubber concentrations of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and metabolites, chlordanes, hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB), and plasma concentrations of thyroid hormones (thyroxine [T4] and tri-iodothyronine [T3]) in free-ranging, newly weaned gray seal pups from the Baltic Sea and the Norwegian waters of the Atlantic Ocean. Concentrations of total T3 (TT3) and free T3 (FT3) were significantly lower in the polluted seals from the Baltic Sea. Blubber concentrations of the sum of the analyzed PCB congeners (sigmaPCBs) and the sum of the DDT compounds (sigmaDDTs) were correlated negatively with plasma TT3 and FT3 concentrations. The results from this study indicate that OCs may affect levels of thyroid hormones in free-ranging gray seal pups, and that more focus should be put on T3 when addressing the possible effects of OCs on thyroid hormone function and status in nonrodent species.

Hormone and metabolite changes associated with extended breeding fasts in male northern elephant seals (Mirounga angustirostris)

“…Individuals with higher DEE exhibited elevations of thyroid across the fast and this was associated with reductions in protein sparing. Thyroid hormones have been demonstrated to vary as a function of age and physiological condition in phocid seals (Boily, 1996;Haulena et al, 1998;Sormo et al, 2005;Stokkan et al, 1995;Woldstad and Jenssen, 1999;Yochem et al, 2008;Bennett et al 2012). Values of tT3 in fasting adult male elephant seals are comparable to values observed in non-molting, adult members of other species of phocid seal, regardless of whether they are fasting or intermittently feeding (see Haulena et al, 1998 for a table providing thyroid hormone values for phocid seals by age and reproductive condition).…”

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

“…As T3 is the active hormone and FT3 represents the biologically available fraction, this may be of concern for the polar bear health. Accordingly, previous studies on mammals reported negative relationships between plasma concentrations of FT3 and PCBs in Svalbard female polar bears with COYs (Braathen et al, 2004), grey seal pups (Halichoerus grypus; Sørmo et al, 2005) and beluga whales (Delphinapterus leucas; Villanger et al, 2011b). Moreover, a study on pregnant women reported low levels of FT3 and TT3 in women with high blood concentrations of PFUnDA and PFDA, respectively, compared to women with low blood concentrations of these compounds (Berg et al, 2015).…”

Stanowisko Polskiego Towarzystwa Endokrynologicznego dotyczące związków endokrynnie czynnych (EDC)

“…PCB congeners can modulate the axis by reducing the response of pituitary cells to TRH [57]. Higher concentrations of organochlorines in the adipose tissue of grey seals correlated with the lower levels of total and free thyroxin [58]. BruckerDavis and Howdeshell published data on the effects of environmental chemicals on thyroid function [59,60].…”

“…Kongenery PCB mogą modulować działanie osi między innymi poprzez obniżenie odpowiedzi komórek przysadki na TRH [57]. Wyższe stężenie organochlorynów w tłuszczu fok szarych korelowało z niższym stężeniem całkowitej i wolnej tyroksyny [58]. Brucker-Davis i Howdeshell opublikowali dane dotyczące wpływu związków chemicznych pochodzących ze środowiska na czynność tarczycy [59,60].…”