triiodothyronine

(trī'ī-ō'dō-thī'rə-nēn', -ī-ŏd'ō-)
n.
A thyroid hormone, C₁₅H₁₂I₃NO₄, similar to thyroxine but more potent, used in the treatment of hypothyroidism.

[TRI- + IODO- + thyronine, an amino acid (THYR(O)- + -ON(E) + -INE²).]

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abbr.: T₃; 3,3,5-triiodo-l-thyronine; one of the hormones secreted by the thyroid gland. Plasma levels of T₃ are much lower than those of thyroxine (T₄) (20-to 50-fold), but the physiological activity of T₃ is higher. Much of T₄ is converted to T₃ within cells. T₃ binds to a thyroid-hormone receptor, which binds to thyroid response element, a transcription-regulatory element. See also thyroglobulin.

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n

A hormone that helps regulate growth and development, control metabolism and body temperature, and by a negativefeedback system, inhibit the secretion of thyrotropin by the pituitary gland.

For a list of words related to triiodothyronine, see:

• Physiology - triiodothyronine: form of thyroxine

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