Objectives: Hyperthyroidism is associated with a high basal metabolic rate and weight loss is a common symptom. However, it has been observed, that once patients are treated, they gain back the lost weight and may also put on more. Given that weight gain is a health factor, theres interest in studying the effect that the thyroid levels have on weight gain and potential harmful health consequences.
Methods: 79 patients (58 female) with hyperthyroidism from thyroid clinic at the University Hospital of Wales were recruited. The mean age was 53 years, IQR 43-67. Premorbid weights and their changes during follow-up (max 24 months) were recorded. Participants were stratified by age and sex. The program STATA was used to apply the Wilcoxon signed-rank test.
Results: At month 0, body weight (mean ± S.D.) was 74.7 kg ± 2.10. During the first 3 months of treatment, there wasnt a significant increase in body weight, but as the time went by, the mean highest weight recorded was 77.8±2.18, which was significantly higher than the baseline weight: P<0.0001.
Conclusion: The data obtained follows what is already known in literature, which is that there is weight gain during treatment for hyperthyroidism. However, in this clinic population, the mean increase in weight was 3.1 kg. Assessment of body composition would be of value to measure the different body components (bone mass, muscle mass and fat mass) and determine what caused the increase in weight. The weight gain is not excessive, so focus interventions such as the involvement of dieticians may not be cost effective. Larger studies are needed to investigate whether different treatments modalities influence weight gain and whether those patients who become hypothyroid during treatment could also have substantially increased risk of excessive weight gain.