Abstract
Background: The most commonly reported symptom of hyperthyroidism is weight loss but successful treatment increases weight. It is not clear if represents replenishment of premorbid weight or overshoot beyond expected regain. Moreover, if there is excessive weight gain, it is unclear whether this is associated with the applied treatment modality. Methods: We analysed 1373 patients with overt hyperthyroidism seen in a secondary care setting. We compared body mass index at initial and discharge visits with the age-sex-matched background population. We modelled longitudinal weight data in relation to treatment modality and thyroid function. Findings: During treatment of hyperthyroidism, men gained 8·0kg (SD±7·5) and women 5·5kg (±6·8). At discharge, there was a significantly increased risk of obesity in male (OR=1·7, 95%CI 1·3¬-2·2, P 10 mIU/L; 0·5kg, 0·3-0·7, P<0·001) or free thyroxine was reduced (fT≤10 pmol/L; 0·3kg, 0·1-0·4, P<0·001) during follow-up. Initiation of levothyroxine was associated with further weight gain (0·4kg, 0·2-0·6, P<0·001) and the predicted excess weight gain in radioiodine-induced hypothyroidism was 1·8kg. Interpretation: Treatment for hyperthyroidism is associated with significant risks of becoming obese. Radioiodine treatment and subsequent development of hypothyroidism were associated with small but significant amounts of excess weight gain compared with antithyroid drugs alone. Funding: Institutional (higher education) Declaration of Interest: All authors declare no conflict of interest. Ethical Approval: The project was 95 approved and registered by the University Hospitals Birmingham NHS Foundation Trust (CARMS-96 11842).
Published Version
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