Propylthiouracil before 131I therapy of hyperthyroid diseases: effect on cure rate evaluated by a randomized clinical trial.

A randomized clinical trial was performed to clarify whether pretreatment with propylthiouracil (PTU) before radioiodine (131I) therapy influences the final outcome of this therapy, as has been indicated by retrospective studies. Untreated consecutive hyperthyroid patients with Graves’ disease (n = 23) or a toxic nodular goiter (n = 57) were randomized to either PTU (+PTU; n = 39) or no pretreatment (−PTU; n = 41) before compensated 131I therapy. The median PTU dose was 100 mg, which was discontinued 4 d before treatment. The median 131I activity was 302 MBq (range, 87–600 MBq). After 131I therapy, the serum free T4 index increased in the +PTU group from 97.7 ± 47.5(±sd) nmol/liter at the time of therapy to 152.3 ± 77.6 nmol/liter at 3 wk (P < 0.001) and 140.4 ± 75.9 nmol/liter at 6 wk (P < 0.001). In the −PTU group, the serum free T4 index, which was initially 254.3 ± 145.7 nmol/liter, decreased significantly to 212.0 ± 113.0 nmol/liter at 3 wk (P < 0.05) and 165.8 ± 110.0 nmol/liter at 6 wk (P < 0.005)....