The effects of persistent organic pollutants (POPs) on thyroid hormones and metabolic rate in exposed herring gull (Larus argentatus) chicks

Abstract

The objectives of the present study were to investigate how plasma concentrations of POPs can affect thyroid hormone levels and basal metabolic rate (BMR) in herring gull (Larus argentatus) chicks. Thyroid hormones are the major controllers of metabolic rate in birds. High concentrations of persistent organic pollutants (POPs) may alter the thyroid hormone homeostasis and subsequently the BMR and limit capacity for adaptive thermogenesis. Captured herring gull chicks were raised and exposed to a natural mixture of POPs. The chicks were starved to mobilize stored fat reserves and increase the POP concentration in blood. Plasma samples were analysed for polychlorinated biphenyls (PCBs), pesticides, polybrominated diphenyl ethers (PBDEs) and metabolites. Additionally, total (T) and free (F) plasma levels of thyroxin (T4) and triiodothyronine (T3) were analysed, and BMR measured. The results of the present study were decreased T3 and FT4 levels and negative associations were observed between TT3-, TT4/FT4 and POP concentrations in exposed-starved herring gull chicks. Positive correlations were observed between FT4/FT3 ratio and POP concentrations, also in exposed starved chicks. No difference in thyroid hormone levels between exposed and control chicks were observed. A positive correlation between FT4-, and a negative correlation between TT4/FT4 and BMR was measured.