Australia: The Land Where Time Began

A biography of the Australian continent 

Australian Aboriginals’ Adaptation to their Environment – Temperature-Responsive of Thyroxine

Thyroxine-binding globulin (TBG) carries and stores thyroxine, the hormone that regulates mammalian metabolism, in the blood. In this paper the authors demonstrate that thyroxine is released from TBG by a temperature-sensitive mechanism, and they also demonstrate how this will provide a homeostatic thyroxine concentration adjustment that matches metabolic needs, as in the case of small animals when hypothermia causes torpor. In conditions such as infections in humans an accelerated release of thyroxine is triggered which results in a 23 % increase in thyroxine concentration at 39^oC. In an environmental adaptation in Aboriginal Australians the in vivo relevance of this fever response is affirmed. The study found how 2 mutations incorporated in the TBG interact in such a way that the surge in thyroxine release will be halved, and therefore the metabolic rate boost that would otherwise occur at body temperatures exceeding 37^oC is prevented. Insights are opened into physiological changes that accompany body temperature variations, as is notable in fevers by the overall findings.

Sources & Further reading

1. Qi, Xiaoqiang, Wee Lee Chan, Randy J. Read, Aiwu Zhou, and Robin W. Carrell. "Temperature-Responsive Release of Thyroxine and Its Environmental Adaptation in Australians." Proceedings of the Royal Society B: Biological Sciences 281, no. 1779 (March 22, 2014 2014).