The simple version for us ordinary folk is here:
The actual paper (abstract, full paper and PDF) available here:
Temperature-responsive release of thyroxine and its environmental adaptation in Australians
Wee Lee Chan1,
Randy J. Read1,
Aiwu Zhou1,2 and
Robin W. Carrell1⇑
+ Author Affiliations
1Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
2Key Laboratory of Cell Differentiation and Apoptosis of Ministry of Education of China, School of Medicine, Shanghai JiaoTong University, No. 280, Shanghai 200025, People's Republic of China
The hormone thyroxine that regulates mammalian metabolism is carried and stored in the blood by thyroxine-binding globulin (TBG). We demonstrate here that the release of thyroxine from TBG occurs by a temperature-sensitive mechanism and show how this will provide a homoeostatic adjustment of the concentration of thyroxine to match metabolic needs, as with the hypothermia and torpor of small animals. In humans, a rise in temperature, as in infections, will trigger an accelerated release of thyroxine, resulting in a predictable 23% increase in the concentration of free thyroxine at 39°C. The in vivo relevance of this fever-response is affirmed in an environmental adaptation in aboriginal Australians. We show how two mutations incorporated in their TBG interact in a way that will halve the surge in thyroxine release, and hence the boost in metabolic rate that would otherwise occur as body temperatures exceed 37°C. The overall findings open insights into physiological changes that accompany variations in body temperature, as notably in fevers.
Received November 26, 2013.
Accepted January 7, 2014.
© 2014 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License creativecommons.org/license... which permits unrestricted use, provided the original author and source are credited.
And this related paper seems to be interesting for the impact of cold on T4 to T3 conversion:
Horm Metab Res. 2014 Jan 20. [Epub ahead of print]
Influence of Chronic Exposure to Cold Environment on Thyroid Gland Function in Rabbits.
Mustafa S1, Elgazzar A2.
1Department of Biomedical Sciences, College of Nursing, Public Authority for Applied Education & Training, Kuwait.
2Department of Nuclear Medicine, Faculty of Medicine, Kuwait University, Kuwait.
Chronic exposure to cold can affect the thyroid gland. However, the effect on thyroid gland perfusion images and the ratio between thyroid hormones secretion were not addressed in any previous study. The present study investigates the effects of chronic cold exposure on thyroid gland function using radionuclide tracer and thyroid hormones secretion concentration. New Zealand white rabbits weighing approximately 1.8-2 kg were kept in a cold room (4°C) for 7 weeks. Thyroid scintigraphy was performed for cold exposed rabbits and a control rabbit group. Each rabbit was injected with 115 MBq (3.1 mCi) technetium-99m pertechnetate (99mTc pertechnetate). Studies were performed using Gamma camera equipped with a low energy, high resolution, pinhole collimator interfaced with a computer. Static images were acquired 20 min after administration of the radiotracer. Rabbits chronically exposed to cold had less body weights than control. Thyroid gland uptake is higher in rabbits chronically exposed to cold than controls using radionuclide perfusion study. The increase was proportional to the time period, so the increase after 7 weeks was greater than 5 weeks. There is also an increase in free triiodothyronine (FT3) and a decrease in free thyroxine (FT4) values. Our results indicate that thyroid gland uptake is higher in rabbits chronically exposed to cold than control and the increase was proportional to the duration. The decrease in rabbit body weights may be related to the increase in metabolism due to the increase of thyroid hormones. Chronic cold exposure also increased the conversion of T4 to T3, which is more potent in thermogenic effect.
© Georg Thieme Verlag KG Stuttgart · New York.
PMID: 24446160 [PubMed - as supplied by publisher]