In 1995 the Royal College of Physicians issued guidelines for the use of radioiodine in hyperthyroidism. They recommended administration of enough radioiodine to achieve euthyroidism, with acceptance of a moderate rate of hypothyroidism e.g. 1520% at 2 years and 13% per annum thereafter. Guide activity was 400550 MBq for standard hyperthyroidism (mainly Graves disease), at least 550 MBq for toxic multinodular goitre, and 300500 MBq in toxic adenoma.
We wished to see if we were achieving the recommended outcomes. We conducted a retrospective audit over 5 years from January 2000 to December 2004. During that time we used a fixed dose of 370 MBq. 351 patients received 390 doses of radioiodine. Mean follow-up was 35 months (166). We reviewed the outcomes of patients who had a diagnosis documented in their case records.
114 patients had documented Graves disease. During follow-up 75 (65.78%) became hypothyroid, 73 (64.03%) within 2 years, 2 (1.75%) within 3 years. 17 (14.91%) remained euthyroid at follow-up. 18 (15.78%) remained hyperthyroid or required up to 2 further doses of radioiodine. 4 patients were lost to follow-up.
57 patients had multinodular goitre. During follow-up 8 (14.03%) became hypothyroid, all within 2 years, 39 (68.42%) remained euthyroid, 10 (17.54%) remained hyperthyroid or required 13 further doses of radioiodine.
16 patients had toxic adenoma, 6 (37.5%) became hypothyroid, all within 2 years, 7 (43.75%) remained euthyroid, 3 (18.75%) required 1 further dose of radioiodine.
Despite using a dose less than that stipulated in the guidelines, our rate of hypothyroidism was higher than recommended for patients with standard hyperthyroidism and within the recommendation for toxic multinodular goitre. Our rate of hypothyroidism was also high for toxic adenoma although there were only 16 patients.