What is the Origin of Active Thyroid Hormone T3?

The term derives from its chemical structure: "triiodo" indicates three iodine atoms attached to the thyronine backbone, a critical component synthesized by the thyroid gland. T3 is largely generated peripherally through the deiodination of the prohormone thyroxine (T4), with the thyroid gland itself producing a smaller, yet significant, amount. Understanding this conversion process is fundamental to clinical endocrinology and managing thyroid health.

What is the Mechanism of Active Thyroid Hormone T3?

T3 exerts its profound influence by entering target cells and binding to specific nuclear thyroid hormone receptors (TRs). This receptor-hormone complex subsequently modulates gene expression, directly affecting the transcription of genes involved in metabolic regulation, growth, and development. The precise regulation of T3 concentration and receptor binding is crucial for maintaining systemic metabolic homeostasis and overall well-being.

Active Thyroid Hormone T3 ∞ Area

Active Thyroid Hormone T3

Meaning

Triiodothyronine, or T3, represents the biologically active form of thyroid hormone, essential for regulating metabolism across virtually all tissues in the human body. This potent hormone is primarily responsible for the thyroid’s physiological effects at the cellular level, impacting energy expenditure, body temperature, and protein synthesis. Clinical assessment often focuses on free T3 levels, which reflect the hormone unbound to transport proteins and readily available to target cells.