Energy balance regulation by thyroid hormones at central level

• Thyroid hormones regulate energy balance and metabolism by acting at the central level.
• Thyroid hormones modulate the autonomous nervous system.
• Thyroid hormones modulate hypothalamic UCP2 and mTOR to regulate feeding.
• Thyroid hormones modulate hypothalamic AMPK to regulate thermogenesis in brown adipose tissue.
• Thyroid hormones act on the hypothalamus to regulate hepatic glucose metabolism.

Classically, medical textbooks taught that most effects of thyroid hormones (THs) on energy homeostasis are directly exerted in peripheral tissues. However, current evidence is changing (and challenging) our perspective about the role of THs from a ‘peripheral’ to a ‘central’ vision, implying that they affect food intake, energy expenditure, and metabolism by acting, to a large extent, at the central level. Interestingly, effects of THs are interrelated with global energy sensors in the central nervous system (CNS), such as uncoupling protein 2 (UCP2), AMP-activated protein kinase (AMPK; the ‘AMPK–BAT axis’), and mechanistic target of rapamycin (mTOR). Here, we review what is currently known about THs and their regulation of energy balance and metabolism in both peripheral and central tissues.