title: Effect of amiodarone on serum T4 and T3 levels in hyperthyroid patients treated with methimazole.
abstract: We investigated the course of thyroid hormones levels in the serum of hyperthyroid patients acutely treated with amiodarone. Ten patients were treated either with amiodarone, 3 X 400 mg daily for 3 days in addition to methimazole, 3 X 20 mg daily for 10 days (Group I; n = 5) or with a placebo plus methimazole at the same doses (Group II; n = 5). Basal T3, T4 and rT3 serum concentrations were: 297 ng/dl, 16.6 micrograms/dl and 507 pg/dl, respectively in Group I and 377 ng/dl, 17.6 micrograms/dl and 362 pg/dl in Group II (NS). Compared with basal values, the drop in serum T3 concentration became significant on Day 1 in Group I, but not until day 5 in Group II. The decrease in serum T3 concentration was significantly higher in Group I than in Group II from Day 1 to Day 7. In Group I, T4 concentration was significantly lower on Days 2, 4 and 6; the percentage drop in T4 calculated from the areas under the curves was higher and the T3/T4 ratio lower on Days 3-5, 7 and 9; rT3 was higher on Days 4 and 5 and its rise was significant on Days 1, 3 and 4. During the follow-up period a transient rise in T4 and T3 concentrations was observed in two patients in Group I when the methimazole dosage was tapered or stopped because of agranulocytosis. In conclusion, in our hyperthyroid patients, amiodarone in conjunction with methimazole induced a greater fall in T3 and T4 than did methimazole alone.
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000638:Amiodarone / Q000097:blood / Q000627:therapeutic use*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood* / Q000188:drug therapy; D008713:Methimazole / Q000627:therapeutic use*; D008875:Middle Aged; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*
chemical_list: D014284:Triiodothyronine; D008713:Methimazole; D000638:Amiodarone; D013974:Thyroxine