Triiodothyronine (T3) (also known as liothyronine) is the active form of the thyroid hormone, thyroxine. Approximately 20% of T3 is secreted into the bloodstream directly by the thyroid gland. The remaining 80% is produced from conversion of thyroxine by organs such as the liver and kidneys. In psychiatry, liothyronine is sometimes used as an augmentation medication for depression in combination with antidepressants.
Liothyronine is the name of the manufactured form of triiodothyronine.
Absorption | 90% absorption, peaks in 1-2 hours (absorption decreases with age) |
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Distribution | 99.8% bound to plasma proteins |
Metabolism | Mainly metabolized in the liver where it is deiodinated to diiodothyronine and monoiodothyronine |
Elimination | Mainly renal |
Half-life | 19 hours |
Substrate of (Metabolized by) | - |
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Induces | - |
Inhibits | CYP3A[1] |
T3 may increase levels of thyrotropin-releasing hormone, corticotrophin releasing factor, and brain derived neurotrophic factor (BDNF).
Starting | Start with 25 mcg daily (12.5mcg in older adults or those with medication sensitivities)[2] |
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Titration | Titrate to 50 mcg daily after at least one week |
Maximum | In depression adjunct studies, doses exceeding 50 mcg have been noted to cause toxicity symptoms. |
Taper | Over a period of 4-8 weeks is recommended. |