Abstract 148 - BEARing with endocrine disruptors: potentially toxic metal(loid)s exposure in European brown bears
Agnieszka Sergiel, Institute of Nature Conservation of Polish Academy of Sciences, Krakow, Poland ProfessionalSalon 8/9
Maja Lazarus, Agnieszka Sergiel, Maja Ferenčaković, Ankica Sekovanić, Slaven
Reljić, Lana Pađen, David M. Janz, Ena Oster, Tomasz Zwijacz-Kozica, Filip Zieba, Nuria Selva,
Djuro Huber
Research addressing potential adverse effects of environmental pollutants on hypothalamic-
pituitary-thyroid (HPT) axis in ursids is crucial in assessing risk of adverse health effects. A
recent study reported alterations in circulating thyroid hormones in polar bears exposed
chronically to inorganic and organic pollutants. We obtained blood from 53 free-ranging
European brown bears (Ursus arctos; Carpathian and Dinara-Pindos populations) trapped
between 2014 and 2019 in order to investigate interrelationships among cadmium, lead, and
mercury, metals with known endocrine disrupting potential, other trace metal(loid)s, free
triiodothyronine (fT3), and free thyroxine (fT4). Ecological, physiological and sampling variables
were taken into consideration while building generalized linear models explaining hormonal
variation. The best model was validated using the corrected Akaike´s Information Criterion
(AICc). Chemiluminescent enzyme immunoassays quantified fT3 and fT4, which ranged <1-3.54
and <30-304 pg/mL, respectively. In top-ranked models, positive contributions of thallium,
sampling year and trap type explained 59-67% of fT3 concentration variation. Models
describing fT4 variation (44-66%) were explained by a positive effect of lead and negative
contributions of copper, selenium and capture day. Furthermore, age group and population
were shown to improve interpretation of fT4 concentrations. Based on these results and
established mechanisms of toxicity, we suggest that lead and thallium might indirectly affect
HPT axis of bears, potentially through enhanced production of reactive oxygen species,
depletion of thiol-rich proteins, or immune suppression. This study suggests that both essential
and non-essential trace metal(loid)s are important variables to be considered when studying
alterations in endocrine physiology in terrestrial wildlife.
