We studied retrospectively the outcome of radioactive iodine therapy (RAI) in 120 thyrotoxic patients with Graves' disease (96 F/ 24 M) who were primarily treated with anti-thyroid drugs (ATD). The decision to use RAI was due either to relapse after ATD-induced remission, lack of compliance on ATD, goiter larger than 60g, old age or association with severe diseases. ATD were discontinued one week before RAI administration, calculated by the formula: glandular volume (g) vs. effective radiation (80 mCi/g of tissue) divided by 24h thyroid uptake (%). We reexamined the patients for 48 months after RAI. Medians of age, goiter size and 24h thyroid uptake were 34y (17-69), 54.5g (20-210) and 73% (21-99), respectively. After RAI, patients became gradually hypothyroid on a rate of 15%/ 6mo until the first 18mo, followed by a rate of 2-5%/ 6mo until the end of 48mo. The number of patients in thyrotoxicosis decreased continuously, being 52.2% 6mo after RAI, 25% after 18mo and 6.7% after 48mo; at the end of the study 8 patients were still thyrotoxic. The total of patients without thyrotoxicosis at the end of observation, that is, the sum of those in euthyroidism and hypothyroidism on T4 therapy ("cure of thyrotoxicosis") reached 46.8% in 6mo, 63.3% in 12mo, 81.7% in 24mo, 87.5% in 36mo and 93.3% in 48mo. Transient hypothyroidism, that is, elevation of TSH higher than 4.5 mU/L until 12mo after RAI, followed by normalization of TSH was found in 7.5% of patients. The following correlations were found in this study: a) initial T3 values and absence of cure of thyroxicosis (p=0.2); b) total RAI doses in relation to time for cure of thyrotoxicosis (p=0.01); c) dose of 131l/thyroid volume in relation to time for cure of thyrotoxicosis (p=0.02). Adverse effects included exarcebation of thyrotoxicosis in 3 patients and pain in the anterior cervical area in one, all reversible and of short duration. Two patients became pregnant after RAI but both gestations and their outcomes were normal.
Thyrotoxicosis; Radioiodine; Graves'dis-ease; 131I; Follow-up
