Comparative effects of sodium ipodate and iodide on serum thyroid hormone concentrations in patients with Graves' disease.

Patients with thyrotoxic Graves' disease were treated daily for 10 d with 1 g sodium ipodate, an iodine rich X-ray contrast agent which impairs outer ring (5'-) deiodination of T4 to T3, or with 12 drops of a saturated solution of potassium iodide (SSKI). T4, T3 and reverse T3 (rT3) concentrations were measured before, during, and 5 and 10 d after the administration of each drug. SSKI therapy induced a decrease in the serum T4 concentration from 14.7 +/- 1.3 microgram/dl (mean +/- SE) to a nadir of 7.9 +/- 0.9 on days 9 and 10 of therapy, all values reaching the normal range by day 9; a decrease in the serum T3 concentration from 402 +/- 43 ng/dl to a nadir of 143 +/- 20 on day 10, remaining elevated in all patients until day 5 and decreasing into the normal range in all except one patient on days 9 and 10; and no change in the serum rT3 concentration. Serum T4 and T3 concentrations returned to baseline values 10 d after withdrawal of SSKI. In contrast sodium ipodate therapy induced only a modest decrease in the serum T4 concentration from 15.1 +/- 0.7 micrograms/dl to a nadir on day 9 of 11.3 +/- 1.0 and serum T4 remained above the normal range in most patients until day 8; a striking and rapid decrease (within 12 h) in ther serum T3 concentration from 340 +/- 36 ng/dl to mean values ranging from 79 to 85 during the last 5 d of therapy, with most values below the normal range during the last 3 d; and a marked increase in the serum rT3 concentration from 111 +/- 15 ng/dl to a peak value of 376 +/- 59 on day 5.(ABSTRACT TRUNCATED AT 250 WORDS)