Often looks like thyroid hormone "controls metabolism" - as if all it does is turn the wick up or down a bit. A few papers now talk about affecting gene expression, usually quite abstractly. My belief is that we will only really see thyroid hormone issues taken seriously when we know what effects thyroid hormones have on individual cells. When specific effects at the molecular level can be shown to translate into physiological processes - and therefore disease or health.
Mol Cell Endocrinol. 2017 Jan 11. pii: S0303-7207(17)30022-9. doi: 10.1016/j.mce.2017.01.018. [Epub ahead of print]
Hypothalamic effects of thyroid hormone.
Zhang Z1, Boelen A1, Bisschop PH1, Kalsbeek A2, Fliers E3.
1Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, The Netherlands.
2Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, The Netherlands; Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, The Netherlands.
3Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, The Netherlands. Electronic address: firstname.lastname@example.org.
Thyroid hormone (TH) is a key driver of metabolism in mammals. Plasma concentrations of TH are kept within a narrow range by negative feedback regulation in the hypothalamus-pituitary-thyroid (HPT) axis. Plasma TH concentrations are an important determinant of metabolic processes in liver and brown adipose tissue (BAT). In addition to endocrine effects of TH derived from the circulation, recent studies have demonstrated additional neural routes for intrahypothalamic thyroid hormone to regulate metabolism in liver and BAT via the sympathetic and parasympathetic branch of the autonomic nervous system (ANS). This review provides an overview of studies reporting metabolic effects of selective administration of T3 within hypothalamic nuclei including the paraventricular nucleus (PVN), the ventromedial nucleus (VMH), the arcuate nucleus (Arc), and the anterior hypothalamic area (AHA). This overview of the literature suggests that intrahypothalamic T3 can have profound effects on hepatic glucose production and insulin sensitivity, energy expenditure in BAT, cardiovascular function and feeding behavior. As the experiments have been performed in experimental animals exclusively, and the timing and route of T3 administration may be an important determinant of effect size, the clinical relevance of these metabolic effects in the chronic setting remains to be established.
Copyright © 2017. Published by Elsevier B.V.
Brown adipose tissue; Cardiovascular function; Glucose; Paraventricular nucleus; Triiodothyronine; Ventromedial nucleus