Thyroid response to blocking sympathetic activity in chronic cold exposed hunters in East Greenland: a case-control study.

IF 3.5 2区医学 Q2 ENDOCRINOLOGY & METABOLISM

European Thyroid Journal Pub Date : 2024-12-01 DOI:10.1530/ETJ-24-0272

Mette Motzfeldt Jensen, Charlotte Almasi, Hans Christian Florian Sørensen, Stine Linding Andersen, Stig Andersen

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Abstract

Background: Thyroid hormones and sympathetic stimulation are needed for activating Brown adipose tissue (BAT) during cold exposure. Studies of human cold exposure have demonstrated both increased production and raised clearance of triiodothyronine (T3). Greenlandic hunters provide a unique model for evaluating metabolic effects of cold exposure.

Aim: We aimed to explore the dynamics of thyroid hormones when blocking sympathetic activity in Greenlandic hunters during winter to inspire knowledge on mechanisms of BAT activation.

Methods: We conducted a 7-day field study of Greenlandic hunters (n=7) in East Greenland in February. The sympathetic system was blocked using a non-selective beta blocker for seven consecutive days. A group of non-hunter Greenlanders (n = 8) from the same settlement were included for parallel sampling. All participants were healthy men. Blood samples were drawn daily for measurement of TSH, thyroid hormone levels, and thyroglobulin.

Results: Hunters had higher serum thyroglobulin, TSH, and high fT3/fT4 ratio compared to controls. Blocking the sympathetic activity was followed by changes in serum thyroglobulin and fT3 with an initial decrease and subsequent restoration of levels, while TSH and fT4 showed a gradual increase over the course of the study. The fT3/fT4 ratio showed a continuous and marked decrease.

Conclusion: We hypothesise that when blocking the sympathetic system, TSH increases to uphold the production of T3 needed for maintaining BAT activity. Additionally, alterations of fT3/fT4-ratio support a hypothesis of adrenergic stimulation promoting T3 over T4 secretion from the thyroid via the adrenergic nerve terminals in the thyroid.

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在东格陵兰岛长期暴露于寒冷的猎人中，甲状腺对阻断交感神经活动的反应：一项病例对照研究。

背景：寒冷暴露时，激活棕色脂肪组织（BAT）需要甲状腺激素和交感神经刺激。人体暴露在寒冷环境下的研究表明，三碘甲状腺原氨酸（T3）的产生和清除都增加了。格陵兰猎人提供了一个独特的模型来评估寒冷暴露对代谢的影响。目的：我们旨在探索甲状腺激素在冬季阻断格陵兰猎人交感神经活动时的动态，以启发对BAT激活机制的认识。方法：我们于2月在东格陵兰岛对格陵兰猎人（n=7）进行了为期7天的实地研究。使用非选择性受体阻滞剂连续7天阻断交感神经系统。来自同一定居点的一组非狩猎格陵兰人（n = 8）被纳入平行抽样。所有参与者都是健康男性。每天抽取血液样本测量TSH、甲状腺激素水平和甲状腺球蛋白。结果：与对照组相比，猎人有更高的血清甲状腺球蛋白、TSH和高fT3/fT4比率。阻断交感神经活动后，血清甲状腺球蛋白和fT3水平发生变化，最初下降，随后恢复，而TSH和fT4在研究过程中逐渐增加。fT3/fT4比值连续显著下降。结论：我们假设当阻断交感神经系统时，TSH增加以维持维持BAT活性所需的T3的产生。此外，fT3/ ft4比值的改变支持了肾上腺素能刺激通过甲状腺的肾上腺素能神经末梢促进甲状腺T3/ T4分泌的假设。

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来源期刊

European Thyroid Journal Medicine-Endocrinology, Diabetes and Metabolism

CiteScore

6.70

自引率

2.10%

发文量

156

期刊介绍： The ''European Thyroid Journal'' publishes papers reporting original research in basic, translational and clinical thyroidology. Original contributions cover all aspects of the field, from molecular and cellular biology to immunology and biochemistry, from physiology to pathology, and from pediatric to adult thyroid diseases with a special focus on thyroid cancer. Readers also benefit from reviews by noted experts, which highlight especially active areas of current research. The journal will further publish formal guidelines in the field, produced and endorsed by the European Thyroid Association.