MALE SEX, AFRICAN AMERICAN RACE OR ETHNICITY, AND TRIIODOTHYRONINE LEVELS AT DIAGNOSIS PREDICT WEIGHT GAIN AFTER ANTITHYROID MEDICATION AND RADIOIODINE THERAPY FOR HYPERTHYROIDISM

Objective: To determine whether racial or ethnic differences affect weight gain after treatment of hyperthyroidism and to reassess established risk factors such as sex, age, and cause of hyperthyroidism. Methods: We conducted a retrospective review of medical records of 111 patients treated with radioiodine (RAT) for hyperthyroidism, with or without preceding antithyroid medication, during 2002 to 2005. We ascertained age, sex, race or ethnicity, insurance status, compliance with visits, serum triiodothyronine (T-3) level at diagnosis, and cause of hyperthyroidism. Weights and serum thyroid-stimulating hormone levels were obtained at diagnosis, at time of RAI therapy, and at 0 to 4 months, 4 to 8 months, 8 to 12 months, and 24 months after RAI treatment. Results: There was a significant weight increase after treatment of hyperthyroidism. Levels of T-3 at initial diagnosis of hyperthyroidism, male sex, and black or Hispanic ethnicity were found to be independent predictors of weight gain after RAI treatment. We found a significant interaction between race or ethnicity and sex in multivariate models. There was no difference in thyroid function across racial or ethnic groups or the sexes. Age, cause of hyperthyroidism, posttreatment thyroid-stimulating hormone level, compliance, and insurance status were not found to be significant predictors of weight gain. Conclusion: The T-3 level at the time of diagnosis of hyperthyroidism is a strong predictor of weight gain after treatment of hyperthyroidism. Black race or ethnicity and male sex are also risk factors for weight gain. (Endocr Pract. 2010;16:609-616)