Background: As thyrotoxicosis is associated with significant morbidity, treatment and ultimately cure is essential. Along with anti-thyroid medication and surgery, the use of radioactive Iodine (I-131) has long been established. However, opinion still varies as to when to use I-131, in which patients and whether to give a fixed or tailored dose. To see if our practice was consistent with published data, we conducted an audit of patients treated with I-131 for benign thyroid disease in our endocrine clinic.
Method: Patients were identified from a database held by the nuclear medicine department. Each received one or more fixed doses of I-131 (400 Mbq) during the study period (Sept 2003 to Sept 2004). Retrospective case note review was performed for 81 consecutive patients: Graves disease (59), Multinodular Goitre (MNG) (19) or undetermined (3), who received a total of 91 doses.
Results: Age (mean±S.D.) women 52.9±17.3, men 51.4±19.9. The number of relapses prior to I-131 therapy varied between zero and three. Cure was defined as either euthyroid on no therapy or hypothyroid requiring T4 replacement. Successful outcome was similar for Graves and MNG (88.1% vs. 89.4%), however hypothyroidism rates were higher in the Graves group (66.1% vs. 36.8%, P<0.01). We also observed a significant increase in weight (kg) (mean±S.D.) from referral to final follow up post I-131 (74.30±14.28 vs. 75.96±16.01, P<0.002).
Conclusion: The use of a fixed dose of 400 Mbq I-131 achieved an overall cure rate of 88.9%, which matches figures in the literature. There was however, a high rate of early hypothyroidism (56.8%). There was also a small yet significant increase in weight following I-131 therapy.