RADIOACTIVE IODINE FOR THE TREATMENT OF H YPERTHYROIDISM IN ADULT PATIENTS

The authors report on their experience with the treatment of hyperthyr oidism using radioiodine (RI) over a period of 15 years in 516 patient s. RI dosimetry was calculated from thyroid 24 hr uptake and weight, u sing linearly increasing RI doses (from 40 to 100 mu Ci/g) with increa sing thyroid weight (between 10 and 100 g) for both diffuse (D) and mu ltinodular (MN) toxic goiters. For solitary toxic (ST) nodules, a fixe d dose of 250 mu Ci/g was used. In severe hyperthyroidism, antithyroid drugs (ATD) and KI (15 mg/d) were added 24 hours after RI and given d uring 1-4 months and 21 days, respectively. Combining RI + ATD/KI ther apy allowed for a reduction of RI recirculation anti release from the gland and also for more rapid return to a euthyroid status. The result s showed that 88 % of patients with ST, 68 % with D, and 55 % with MN were cured with a single dose of RI. Furthermore, the incidence of lat e hypothyroidism was relatively low reaching 7 % in ST, 36 % in D, and 28 % in MN after a follow-up period of fifteen rears. Annual follow-u p, however showed that an additional 2.7 % of patients (3.5 % of D; 1. 6 % of MN ; 2.4 % of ST) exhibited - per year - an exaggerated TSH res ponse to TRH even though these patients remained clinically and bioche mically euthyroid (normal circulating basal hormones and TSH levels). In conclusion 1) low doses RI combined with ATD/KI yielded a high succ ess rate : less than 30 % of patients required more than 1 dose and on ly 30 % became hyporthyroid after prolonged follow-up; 2) abnormalitie s of TRH test were not infrequent in patients with D and MN goiters, a s well as ST nodules, thereby fully justifying the need for careful an d prolonged follow-up of all hyperthyroid patients receiving RI therap y.