Desiccated thyroid is dried, powdered pig thyroid gland, which contains both thyroid hormones, T4 (levothyroxine) and T3 (liothyronine). Armour Thyroid is the best-known brand; each grain (60 mg) provides 38 mcg of T4 and 9 mcg of T3. It is used to treat an underactive thyroid, and its label says it has not been approved by FDA as a new drug.
Also known as: Armour Thyroid, NDT, natural desiccated thyroid, thyroid tablets USP.
Armour Thyroid comes as 15 mg (1/4 grain), 30 mg (1/2 grain), 60 mg (1 grain), 90 mg (1 1/2 grains), 120 mg (2 grains), 180 mg (3 grains), 240 mg (4 grains) and 300 mg (5 grains) tablets.
The Armour Thyroid label lists it for an underactive thyroid of any cause (except the temporary kind during recovery from subacute thyroiditis) and to suppress TSH in some goiters, thyroid nodules, Hashimoto's thyroiditis and thyroid cancer. A footnote on the label says it "has not been approved by FDA as a new drug." The usual starting dose is 30 mg, raised by 15 mg every 2 to 3 weeks (15 mg to start with long-standing myxedema, a severe form of hypothyroidism, especially if heart problems are suspected); most people need 60 to 120 mg a day, and doses are set by symptoms and blood tests.
The label warns that thyroid hormones should not be used for weight loss: normal doses do not cause it in people with normal thyroid function, and larger doses can cause serious or life-threatening toxicity. It is not used with untreated adrenal insufficiency or an overactive thyroid. Biotin supplements can throw off thyroid blood tests, so the label says to stop biotin at least 2 days before testing. Because it comes from pig thyroid made in a facility that also handles cow tissue, the label notes a theoretical risk of animal viruses; no cases have been reported. See also levothyroxine and liothyronine.
The Armour Thyroid label says the hormones in desiccated thyroid are absorbed like the synthetic ones: 48% to 79% of T4 is absorbed (more when fasting), and about 95% of T3 is absorbed within 4 hours. T4 binds more tightly to blood proteins and lasts longer than T3. The label does not give a half-life for the tablet, so we do not list one; see the levothyroxine and liothyronine guides for those hormones.
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