[Effect of low-dose amiodarone on thyroid function].
Thyroid function was examined periodically in a group of 85 patients treated with low-dose amiodarone, and followed for 1-13 years (mean 3.6). Biochemical hypothyroidism (elevated thyroid stimulating hormone (TSH) only) developed in 8 patients and clinical hypothyroidism in 3, while hypothyroidism developed in 5. In the first 11 cases amiodarone was continued but 1-thyroxine was added. In the 5 that became hyperthyroid, amiodarone was stopped and thyroid function became normal within a few months. In the 69 patients without thyroid dysfunction, elevated thyroxine (T4) and free thyroxine index (FTI) were found in 20% and 17%, respectively, and elevated free T4 (FT4) in 28%; all had normal total tri-iodothyronine (TT3) and TSH. In practically all patients, reverse T3 (rT3) rose more than 30% above initial levels. It is concluded that in patients treated with low dose amiodarone: 1) thyroid function should be followed closely; 2) elevated levels of TT4, FTI and FT4 do not necessarily imply hyperthyroidism; 3) hypothyroidism may be biochemical only, without progression to overt hypothyroidism, despite continued treatment; 4) both the hypo- and the hyperthyroidism induced are usually reversible; 5) amiodarone may be continued despite onset of hypothyroidism, provided replacement therapy is given.
Dept. of Medicine D, Edith Wolfson Medical Center, Holon.
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D
Feigl
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R
Gilad
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M
Tuwal
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Nakash
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E
Katz
D000638:Amiodarone / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D005500:Follow-Up Studies; D006801:Humans; D006980:Hyperthyroidism / Q000139:chemically induced; D007037:Hypothyroidism / Q000139:chemically induced / Q000188:drug therapy; D013961:Thyroid Gland / Q000187:drug effects*; D013963:Thyroid Hormones / Q000097:blood; D013974:Thyroxine / Q000627:therapeutic use
D013963:Thyroid Hormones; D000638:Amiodarone; D013974:Thyroxine