Remission in children with hyperthyroidism treated with propylthiouracil. Long-term results.

We treated 69 hyperthyroid children with propylthiouracil, of whom 53 remained under surveillance. Of these children, 34 (64%) had an initial remission, but relapses were frequent (47%). At this writing, 24 patients (45%) were in remission, with a mean duration of remission of 55 months (range, ten to 132 months). We found that the triiodothyronine level took significantly longer than the thyroxine (T4) level to return to normal. Thus, based on the T4 level alone, treatment may have been stopped prematurely in some patients, causing the relapse rate to be falsely high. The response to therapy did not depend on the size of the goiter nor on the initial levels of T4 or triiodothyronine. Six patients had adverse reactions, which were serious in two patients.