Effect of Levo-Thyroxine Treatment on Weight and Body Mass Index in Children with Acquired Hypothyroidism

Objective: To determine whether normalization of thyroid-stimulating hormone (TSH) in children with acquired hypothyroidism is associated with a decrease in weight or body mass index (BMI). Study design: We retrospectively identified 68 subjects with acquired hypothyroidism who were seen at least once in our center in follow-up between 1995 and 2006. Results: Treatment with levo-thyroxine decreased the mean TSH level from 147 μU/mL initially to 5.0 μU/mL at the second visit 4.4 months later. This was not associated with a significant change in weight or BMI. Of the 68 subjects, 31% lost weight by the second visit (mean 2.3 kg). The mean initial TSH level of this group was 349 μU/mL. Thirty of the 68 children had at least 2 years of follow-up, and 19/68 had at least 4 years of follow-up. Over those intervals, weight and BMI percentiles and z scores did not change significantly from baseline values. Conclusions: Most children treated for acquired hypothyroidism exhibited little short-term or long-term change in weight or BMI despite near-normalization of TSH. Those children who lost weight tended to have severe hypothyroidism and to have only a small weight loss. Consequently, practitioners should not expect significant decreases in weight after treatment in most children with hypothyroidism.