Further studies on the long-term treatment of Graves' hyperthyroidism with ipodate: assessment of a minimal effective dose.

We have previously described that sodium ipodate (500 mg/day, p.o.) is effective in normalizing serum T3 and T4 levels in most patients with Graves' hyperthyroidism. In this study, we examined serum T3, T4, and rT3 levels in 14 hyperthyroid patients with Graves' disease during treatment with a lower dose (500 mg, every other day, p.o.) of sodium ipodate for a period of 3-30 weeks (mean 15.5 weeks). Three types of responses were observed. In group I (4 patients), both serum T3 and T4 were in the normal range at the end of treatment [baseline: mean +/- SEM T3, 6.8 +/- 0.96 nmol/L (normal 0.92-3.0)] and T4 [256 +/- 44 nmol/L (normal 62-167); post-ipodate: T3, 2.0 +/- 0.46 nmol/L and T4 107 +/- 28 nmol/L]. In group II (n = 5), either serum T3 (3 patients) or serum T4 (2 patients) did not become normal (baseline: T3 7.7 +/- 1.1 and T4 228 +/- 3.9; post-ipodate: T3 2.9 +/- 0.57 and T4 188 +/- 27 nmol/L). In group III (5 patients), neither serum T3 nor serum T4 returned to normal following ipodate treatment (baseline: T3 11.9 +/- 1.8 and T4 260 +/- 23; post-ipodate: T3 7.5 +/- 0.49 and T4 322 +/- 17 nmol/L). The mean serum rT3 concentration increased during ipodate treatment to a peak value of 100% above baseline and remained elevated (20-75% above baseline) throughout the study. Some improvement in hyperthyroidism was suggested by increase in body weight during ipodate treatment in most cases.(ABSTRACT TRUNCATED AT 250 WORDS)