TRH/TSH/Thyroid hormone

Thyroid hormone production • A decline in metabolic rate caused by increased metabolic need or physical exertion stimulates the production of thyrotropin hormone releasing (TRH) hormone from the cells of the hypothalamus. • Thyrotropin hormone releasing hormone targets the thyrotrophic cells in the anterior pituitary and causes them to release thyroid stimulating hormone (TSH). • Thyroid stimulating hormone targets the follicular cells of the thyroid gland causing them to produce thyroid hormones (T3 and T4). Metabolism and body temperature • The thyroid hormones target body cells. • Increased thyroid hormones: • increase oxygen use and basal metabolic rate. • increase cellular metabolism by increasing glucose catabolism ( production of more ATP) - this also results in increased body temperature. • increase lipolysis to provide cells with energy for cellular metabolism from lipids. • The overall result would be an increase in oxygen, lipid and glucose use to fuel a faster metabolic rate. The increased metabolism will result in increased body temperature. Cardiovascular stimulation • The thyroid hormones target muscle cells in blood vessels and heart. • Increased thyroid hormones: • increase vasoconstriction of blood vessels thereby increasing blood pressure. • increase contraction of heart muscle thereby increasing blood pressure. • Increased blood pressure and flow increases delivery of fuel molecules and oxygen to cells thereby supporting higher metabolic rate. Protein synthesis and development • The thyroid hormones target skeletal cells, muscular cells and especially cells of the nervous system, during growth and development. • Increased thyroid hormones increase protein synthesis providing a metabolic rate necessary for normal growth and development of skeletal, muscular and nervous systems.

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