Endocrine Abstracts

Background: Radioiodine therapy (I-131) is commonly prescribed for benign thyroid disease in keeping with recommended guidelines.

Aims: To determine the effectiveness of I-131 in treating benign thyroid disease and the rates of hypothyroidism following treatment and by diagnosis.

Methods: We identified 100 patients who received radioiodine therapy between November 2013 and June 2015 from a database held in the Medical Physics Department at the University Hospital of Wales, Cardiff, UK. Patient group: 18 male, 82 female; mean age: 58 (15-91)y. Mean activity of I-131 administered: 556 (529-572) MBq. Diagnosis: Graves’ disease (52%), solitary toxic nodule (15%), toxic multinodular goitre (MNG) (21%), subclinical hyperthyroidism (12%). 89% were cured with a single treatment of I-131, 10% required a second therapy and 1% a third. Hypothyroidism: 67% patients became hypothyroid, requiring levothyroxine replacement. Rates of hypothyroidism according to diagnosis: Graves’ (49/52 = 94%), solitary toxic nodule (6/15 = 40%), toxic MNG (7/21 = 33%), subclinical hyperthyroidism (5/12 = 42%), X 2 (6, n=100) = 40.06, P<.001. There was no correlation between development of hypothyroidism and smoking status or age. Median time to hypothyroidism was 4 (1-94) months, mode 2 months. There was no correlation between time to hypothyroidism and smoking status or age.

Conclusions: Most patients who received I-131 were female, and had a a diagnosis of Graves’ disease. 89% were cured with following a single treatment of I-131, and overall 67% became hypothyroid, most 2 months following therapy. There was a statistically significant different in the rates of those who became hypothyroid according to diagnosis, with the highest rates of hypothyroidism in those receiving I-131 for Graves’ disease.