Hyperthyroidism and radio-iodine therapy in a district general hospital

A retrospective analysis was performed of 48 patients with hyperthyroidism (41 women aged 35-80, mean 56.6 years; 7 men aged 31-77, mean 52.1 years) treated with a fixed dose of 550 MBq 131I during a 12 month period May 1991-April 1992. Weight loss was common at presentation but 28.57% of women aged 35-49 years weighed over 80 kg compared to 9.98% in a standard UK population P < 0.05. Patients treated with carbimazole (73%) prior to 131I had higher FT3 levels at presentation (14.0 +/- 4.4 pmol/l) compared to those (27%) who were considered not to require such treatment (8.9 +/- 1.4 pmol/l, P < 0.001). Four months following radio-iodine, 67% were hypothyroid, 25% were euthyroid and 8% remained thyrotoxic and were retreated. Another patient became hypothyroid during 1 year of follow-up. Pre-treatment with carbimazole did not protect against the development of hypothyroidism (carbimazole treated 69% hypothyroid at 4 months, untreated 62% hypothyroid at 4 months). Patients with continuing thyrotoxicosis had very high FT3 levels at presentation (18.6, 21.1, 20 and in one patient reported only as > 10 pmol/l). A rationalized programme of follow-up assessments at 2, 3, 4, 8 and 12 months is suggested for patients treated with this dose of radio-iodine.