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Type 2 Deiodinase

Meaning

Type 2 Deiodinase (D2) is a selenocysteine-containing enzyme that is critically responsible for the local, intracellular activation of thyroid hormone by converting the relatively inactive prohormone thyroxine ($T_4$) into the highly potent, biologically active triiodothyronine ($T_3$). This enzyme is predominantly expressed in key metabolic and neuroendocrine tissues, including the brain, pituitary gland, brown adipose tissue, and skeletal muscle. It serves as a vital regulatory point for maintaining a stable and appropriate supply of active thyroid hormone at the cellular level.