甲状腺ホルモンの機能

The thyroid hormone, or TH, is essential for the normal development and maturation of the skeletal, muscular, and nervous systems during fetal and childhood growth. TH accelerates bone mineral turnover and regulates protein synthesis in developing tissues.

Once a person reaches adulthood, TH influences the reproductive system by regulating gonadal hormone secretion and stimulating endocrine tissue.

TH also affects the circulatory system by promoting normal heart function, red blood cell synthesis, and tissue oxygenation.

TH binds to and can be stored by the cell's cytoplasmic receptors. These receptors release the hormone when intracellular levels of TH decrease to maintain cellular homeostasis.

Additionally, the hormone can bind to nuclear and mitochondrial membrane receptors. 

In the nucleus, TH activates the genes for enzymes involved in glycolysis and ATP production. In the mitochondria, it directly increases ATP production.

The combined effects of thyroid hormone in the nucleus and mitochondria result in an elevated cellular metabolic rate, also known as the calorigenic effect.