Duration of antithyroid drug treatment may predict weight gain after radioactive iodine therapy in patients with Graves’ disease

Abstract

BackgroundWeight gain post-radioiodine (RAI) treatment is observed in patients with hyperthyroid Graves’ disease. Previous studies, mostly in Caucasian patients, demonstrated excessive weight gain averaging 5–7 kg from initial presentation. AimThe aim of this study was to determine the extent and risk factors of weight gain in Thai patients with RAI-treated Graves’ disease. MethodsThis was a 5-year retrospective study of patients with hyperthyroid Graves’ disease who received RAI treatment during 2016–2020. The proportion and associated risk factors of weight gain ≥5% in patients who was followed for at least 3 months when compared with weight at RAI administration were analyzed. ResultsThere were 347 patients with Graves’ disease (females 81.0%, mean age 38.8 ± 12.1 years, BMI 23.3 ± 4.0 kg/m2) who were treated with RAI. Almost all RAI-treated patients (91.9%) eventually developed hypothyroidism. During the median follow-up period of 25 months, 73.1% of them had weight gain. The mean weight change was +2.5 ± 4.9 kgs when compared with weight at the time RAI administration and +3.4 ± 6.5 kgs when compared with recalled body weight before the onset of hyperthyroidism. The proportion of patient in the obesity class I (BMI 25.0–29.9 kg/m2) increased from 23.6% to 28.0% and obesity class II (BMI ≥30.0 kg/m2) increased from 5.2% to 8.9%. Duration of antithyroid drug treatment less than 6 months after the diagnosis of hyperthyroidism was the only factor associated with weight gain ≥5%. ConclusionsWeight gain post-RAI treatment was common, and a significant proportion of patients went on to develop obesity. Early intervention with weight management support should be employed in patients with less than 6 months of antithyroid drug treatment before RAI.