Hypothyroidism in hibernating brown bears

Thyroid Research

Brief Report

Malene Brohus¹  Anne Mette Frøbert¹  Michael T. Overgaard¹  Claus G. Nielsen²  Jonas Kindberg³  Ole Fröbert⁴ 

[1] Department of Chemistry and Bioscience, Faculty of Engineering and Science, Aalborg University, Fredrik Bajers Vej 7H, 9220, Aalborg East, Denmark;Department of Clinical Biochemistry, Aalborg University Hospital, Aalborg, Denmark;Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden;Norwegian Institute for Nature Research, Trondheim, Norway;Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus, Denmark;Department of Cardiology, Faculty of Health, Örebro University, Örebro, Sweden;Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark;Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus, Denmark;

关键词: Thyroid hormone;    Thyroxine;    Triiodothyronine;    Thyroxine-binding globulin (TBG);    Ursus arctos;    Hibernation;    Hypothyroidism;    Metabolism;   

DOI  :  10.1186/s13044-022-00144-2

 received in 2022-07-07, accepted in 2022-12-11,  发布年份 2022

来源: Springer

【 摘 要 】

Brown bears hibernate throughout half of the year as a survival strategy to reduce energy consumption during prolonged periods with scarcity of food and water. Thyroid hormones are the major endocrine regulators of basal metabolic rate in humans. Therefore, we aimed to determine regulations in serum thyroid hormone levels in hibernation compared to the active state to investigate if these are involved in the adaptions for hibernation.We used electrochemiluminescence immunoassay to quantify total triiodothyronine (T3) and thyroxine (T4) levels in hibernation and active state in paired serum samples from six subadult Scandinavian brown bears. Additionally, we determined regulations in the liver mRNA levels of three major thyroid hormone-binding proteins; thyroxine-binding globulin (TBG), transthyretin (TTR), and albumin, by analysis of previously published grizzly bear RNA sequencing data.We found that bears were hypothyroid when hibernating with T4 levels reduced to less than 44% (P = 0.008) and T3 levels reduced to less than 36% (P = 0.016) of those measured in the active state. In hibernation, mRNA levels of TBG and albumin increased to 449% (P = 0.031) and 121% (P = 0.031), respectively, of those measured in the active state. TTR mRNA levels did not change.Hibernating bears are hypothyroid and share physiologic features with hypothyroid humans, including decreased basal metabolic rate, bradycardia, hypothermia, and fatigue. We speculate that decreased thyroid hormone signaling is a key mediator of hibernation physiology in bears. Our findings shed light on the translational potential of bear hibernation physiology to humans for whom a similar hypometabolic state could be of interest in specific conditions.

【 授权许可】

CC BY   
© The Author(s) 2023

【 图 表 】

Fig. 2

Fig. 2