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T3

Meaning

T3, or triiodothyronine, is the biologically most active and potent form of the thyroid hormone, playing an absolutely pivotal role in regulating the body’s systemic metabolic rate, cardiac contractility, digestive motility, muscle function, and overall brain development and maintenance. While the thyroid gland secretes a small amount of T3 directly, the vast majority of the circulating hormone is generated peripherally through the enzymatic deiodination of the prohormone thyroxine (T4) in various tissues. Its profound potency and rapid onset of action make it a critical therapeutic agent in specific, clinically determined cases of hypothyroidism.