The occurrence of hypothyroidism following radioactive iodine treatment of toxic nodular goiter is related to the TSH level

Background Strategies to increase frequency of euthyroidism following radioactive (RAI) treatment of hyperthyroidism are required. Aims To examine the role of TSH in development of hypothyroidism post RAI treatment in patients with Graves’ disease ( N = 98) or toxic nodular goiter, TNG ( N = 88). Design This retrospective study examined thyroid status over a mean of 3.7 years post-RAI. Results Although RAI dose was significantly higher in TNG group, hypothyroidism occurred more frequently in Graves’ disease (71.4 and 22.7%) P < 0.001. The TSH levels at the time of RAI treatment were lower in TNG patients who remained euthyroid, ( 0.4±0.1 vs. 1.2±0.5 mU/l, P < 0.0022). Conclusions A higher frequency of euthyroidism occurs in patients with TNG than with Graves’ disease following RAI , particularly when suppressed TSH levels were suppressed at time of RAI-treatment.