Radioiodine therapy in thyrotoxicosis

One hundred and two patients (81 females, 21 males) suffering from thyrotoxicosis as diagnosed clinically and confirmed by laboratory investigations including the estimation of thyroid hormones in blood were treated with radioiodine (I-131) at the University of Minnesota Hospital between 1976 and 1986. Nine (9%) patients needed two and 3 (3%) patients needed three therapeutic doses of I-131. The age range of the patients was 17-82 years (mean 43, SD 17). The doses of I-131 administered ranged from 3.9 to 100 mCi (mean 13.7). Twenty of these patients received a relatively high dose from 20 to 100 mCi. The others were given smaller calculated doses based on radioiodine uptake and thyroid size is determined by palpation and nuclear scans. Of the 73 patients for whom follow-up information was available, 66 (90%) eventually became hypothyroid as judged by clinical criteria. These data also suggest that the incidence of hypothyroidism is quite independent of the dose (microCi/g thyroid) administered.