Medical Use
Both T3 and T4 are used to treat thyroid hormone deficiency (hypothyroidism). They are both absorbed well by the gut, so can be given orally. Levothyroxine is the pharmaceutical name (INN) of physiological thyroxine (T4), which is metabolised more slowly than T3 and hence usually only needs once-daily administration. Natural desiccated thyroid hormones are derived from pig thyroid glands, and are a "natural" hypothyroid treatment containing 20% T3 and traces of T2, T1 and calcitonin. Also available are synthetic combinations of T3/T4 in different ratios (such as liotrix) and pure-T3 medications (INN: liothyronine). Levothyroxine is usually the first course of treatment tried. Some patients feel they do better on desiccated thyroid hormones, however, this is based on anecdotal evidence and no clinical trials have shown any benefit over the biosynthetic forms.
Thyronamines have no medical usages yet, though their use has been proposed for controlled induction of hypothermia, which causes the brain to enter a protective cycle, useful in preventing damage during ischemic shock.
Synthetic thyroxine was first successfully produced by Charles Robert Harington and George Barger in 1926.
Read more about this topic: Thyroid Hormone
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