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Thyroid Medications (cont.)

Other Thyroid Hormone Replacements

L-triiodothyronine

  • Also known as T3 [(liothyronine (Cytomel)]
    • T3 has a very short half life and must be given two to three times each day
    • T3 is responsible for most of the functions of thyroid hormone. Most of T3 comes from the conversion T4 (either from the thyroid gland or from L-thyroxine administration) to T3
    • However, T3 is seldom used alone for the treatment of hypothyroidism
    • T3 is rarely used in combination with LT4 for the treatment of hypothyroidism, but carefully controlled studies in the United States have not shown any benefit from this combined therapy
    • T3 is used for short term therapy during the preparation of patients with thyroid cancer for diagnostic imaging or radioactive iodine treatment
  • Desiccated animal (pig) "natural" thyroid extract [(thyroid (desiccated) (Armour Thyroid, Westhroid)]
    • Contains both T3 and T4, though not in the same proportions as the human thyroid gland; this extract contains excess T3 compared to the amount of T4 for human physiology
    • The proportions of T3 and T4 may vary from bottle to bottle of Armour thyroid
    • Extract should not be prescribed for the treatment of hypothyroidism
    • There is no current practical use for extract in thyroid care
Medically Reviewed by a Doctor on 12/2/2015

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