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Thyroid Function T3 T4

Meaning

Thyroid Function T3 T4 refers to the clinical assessment of the synthesis, secretion, and peripheral metabolism of the two primary thyroid hormones: Thyroxine (T4) and Triiodothyronine (T3), which are central regulators of basal metabolic rate and cellular energy expenditure. T4 is the prohormone, secreted in the largest quantity, while T3 is the biologically active form that binds to nuclear receptors to exert its physiological effects. Comprehensive evaluation of this function requires measuring free and total levels of both hormones, along with TSH, to understand the entire Hypothalamic-Pituitary-Thyroid (HPT) axis.