Effects of thyroid hormones on thermogenesis and energy partitioning

Abstract

21Thyroid hormones (TH) are of central importance for thermogenesis, energy homeostasis, 22and metabolism. Here we will discuss these aspects by focussing on the physiological 23 aspects of TH-dependent regulation in response to cold exposure and fasting which will be 24 compared to alterations in primary hyper-and hypothyroidism. In particular, we will 25 summarise current knowledge on regional thyroid hormone status in the central nervous 26 system (CNS) and in peripheral cells. In contrast to hyper-and hypothyroidism, where 27 parallel changes are observed, local alterations in the CNS differ to peripheral compartments 28 when induced by cold exposure or fasting. Cold exposure is associated with low 29 hypothalamic TH concentrations but increased TH levels in the periphery. Fasting results in a 30 reversed TH pattern. Primary hypothyroidism and hyperthyroidism disrupt these fine-tuned 31 adaptive mechanisms and both, the hypothalamus and the periphery, will have the same TH 32 status. These important mechanisms need to be considered when discussing thyroid 33 hormone replacement and other therapeutical interventions to modulate TH status. 34

Effects of Propranolol on Bone, White Adipose Tissue, and Bone Marrow Adipose Tissue in Mice Housed at Room Temperature or Thermoneutral Temperature

“…Elevated glucocorticoid and thyroid hormone levels, and decreased leptin levels may contribute to the rapid cancellous bone loss observed in male and female mice housed at room temperature. Glucocorticoids, thyroid hormone and leptin are important regulators of bone metabolism and their levels are altered by housing temperature (62)(63)(64)(65)(66)(67)(68)(69). Further research is required to establish the role of changes in these hormones in premature cancellous bone loss in mice housed at sub-thermoneutral temperatures.…”

Circulating Concentrations of GDF11 are Positively Associated with TSH Levels in Humans

“…Thyroid hormone signaling takes place peripherally, mostly in the liver, white and brown adipose tissues, but also centrally, in the hypothalamus [1,2]. Thyroid hormones directly stimulate energy expenditure changing the functionality and increasing the expression of genes involved in thermogenesis, such as uncoupling protein 1, in peripheral tissues such as skeletal muscle and brown adipose tissue (BAT), but also through central actions [3].…”

Humans in the cold: Regulating energy balance

“…When exposed to decreased temperatures, cold‐sensitive thermoreceptors activate the sympathetic nervous system (SNS), stimulating the release of norepinephrine, resulting in downstream lipolysis and release of free fatty acids. CE also results in decreases in triiodothyronine (T3) in the brain, further exciting the SNS and inhibiting the agouti‐related peptide neurons, an effect linked to decreases in appetite and EI, which has been previously explained in more detail . Conversely, peripheral T3 increases with CE, resulting in increases in thermogenesis.…”

“…CE also results in decreases in triiodothyronine (T3) in the brain, further exciting the SNS and inhibiting the agouti‐related peptide neurons, an effect linked to decreases in appetite and EI, which has been previously explained in more detail . Conversely, peripheral T3 increases with CE, resulting in increases in thermogenesis. Studies in a variety of rodent species found significant increases in norepinephrine turnover, plasma norepinephrine, or urinary norepinephrine following a CE stimulus between 3 and 6°C.…”