The early development of hypothyroidism after 131I treatment for hyperthyroid Graves' disease

827 patients with Graves' hyperthyroidism following 131I treatment were followed up at 3 monthly intervals for 12∼36 months from 1985 to 1991. Physical examination and serum total T3, T4, TSH measurements were made at each visit. According to the authors data, 90% early hypothyroidism occurred within 2∼3 months after 131I treatment, thereby, careful follow-up study is very important during this period. T4 was much more sensitive than T3 in diagnosing early hypothyroidism, while the TSH level shows thyroid reservation function, and is less sensitive than T4 in diagnosing 131I induced hypothyroidism. The study confirmed the view that the early incidence of post 131I therapy hypothyroidism was strongly dose dependent