For the last several years, we have been monitoring the bioaccumulation of trace elements with endocrine-disrupting potential (so-called endocrine disruptors) in brown bears. With another study in this line, we aimed at assessing circulating levels of reproductive, stress, and thyroid hormones in relation to arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb) and thallium (Tl) in blood samples from 53 free-ranging brown bears from two European populations (Carpathian and Dinara-Pindos). Our goal was to further investigate linkages between toxic trace elements exposure and potentially adverse ecological effects in these two bear populations. The effects of investigated elements can pose potential risks to the fitness and survival of the species through their impact on reproduction success and overall health, and thus its determination is relevant to the conservation of this species. We also provide the first data on reproductive, stress and thyroid hormone levels in the blood of free-ranging European brown bears, acknowledging physiological and environmental factors underlying its variation.
We found a positive association between cortisol and Cd, and a negative association with Tl. In addition, Tl and Pb were identified as key factors in explaining variation in thyroid hormones (free triiodothyronine fT3 and free thyroxine fT4). Presented results may imply impacts of anthropogenic trace elements contamination on stress and immune response, growth and differentiation, development, reproduction, thermoregulation and metabolism being all vital functions regulated by thyroid hormones and cortisol. However, for more straightforward evidence of heavy metals’ effects on the endocrine system, we recommend the inclusion of more sensitive and specific biomarkers of endocrine disruption on a larger sample scale in future studies.
In this study, we collaborated with our colleagues from the Institute for Medical Research and Occupational Health, Faculty of Veterinary Medicine and Faculty of Agricultural Sciences in Zagreb (Croatia), Department of Veterinary Biomedical Sciences of the University of Saskatchewan (Canada) and Tatra National Park. More details can be found here https://www.sciencedirect.com/science/article/pii/S0048969724076435?via%3Dihub
By Agnieszka Sergiel