Cold Exposure Distinctively Modulates Parathyroid and Thyroid Hormones in Cold-Acclimatized and Non-Acclimatized Humans.

Institute of Experimental Endocrinology, Biomedical Research Center, Slovak Academy of Sciences, Bratislava, Slovakia. Institute of Pathophysiology, Faculty of Medicine, Comenius University, Bratislava, Slovakia. Department of Health Sciences and Technology, Institute of Food, Nutrition and Health ETH Zürich, Schwerzenbach, Switzerland. Department of Otorhinolaryngology - Head and Neck Surgery, Faculty of Medicine Comenius University and University Hospital Bratislava, Bratislava, Slovakia. Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria. Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria. Department of Endocrinology, Diabetes & Metabolism, University Hospital of Basel, Basel, Switzerland. Department of Nuclear Medicine, University Hospital Zürich, Zürich, Switzerland. Faculty of Physical Education and Sports, Comenius University, Bratislava, Slovakia.

Endocrinology. 2020;(7)

Abstract

Cold-induced activation of thermogenesis modulates energy metabolism, but the role of humoral mediators is not completely understood. We aimed to investigate the role of parathyroid and thyroid hormones in acute and adaptive response to cold in humans. Examinations were performed before/after 15 minutes of ice-water swimming (n = 15) or 120 to 150 minutes of cold-induced nonshivering thermogenesis (NST) applied to cold-acclimatized (n = 6) or non-acclimatized (n = 11) individuals. Deep-neck brown adipose tissue (BAT) was collected from non-acclimatized patients undergoing elective neck surgery (n = 36). Seasonal variations in metabolic/hormonal parameters of ice-water swimmers were evaluated. We found that in ice-water swimmers, PTH and TSH increased and free T3, T4 decreased after a 15-minute winter swim, whereas NST-inducing cold exposure failed to regulate PTH and free T4 and lowered TSH and free T3. Ice-water swimming-induced increase in PTH correlated negatively with systemic calcium and positively with phosphorus. In non-acclimatized men, NST-inducing cold decreased PTH and TSH. Positive correlation between systemic levels of PTH and whole-body metabolic preference for lipids as well as BAT volume was found across the 2 populations. Moreover, NST-cooling protocol-induced changes in metabolic preference for lipids correlated positively with changes in PTH. Finally, variability in circulating PTH correlated positively with UCP1/UCP1, PPARGC1A, and DIO2 in BAT from neck surgery patients. Our data suggest that regulation of PTH and thyroid hormones during cold exposure in humans varies by cold acclimatization level and/or cold stimulus intensity. Possible role of PTH in NST is indicated by its positive relationships with whole-body metabolic preference for lipids, BAT volume, and UCP1 content.