Obesity-related subclinical hypothyroidism in childhood: Elevated triglycerides but not basal metabolic rate.

Background: Studies on the associations between obesity-related subclinical hypothyroidism with basal metabolic rate and risk factors of cardiovascular disease in children and adolescents are scarce.

Methods: Retrospective cohort study of children with obesity (n = 294) from the Uppsala Longitudinal Study of Childhood Obesity cohort. Differences in basal metabolic rate quantified by indirect calorimetry, and the cardiovascular risk factors; body mass index, blood lipids, fasting and 2 h oral glucose tolerance test glucose, glycated haemoglobin and insulin resistance, between subjects with and without subclinical hypothyroidism were investigated. The associations of baseline thyroid stimulating hormone (TSH) and ΔTSH with change in cardiovascular risk factors over time were assessed.

Results: Subjects with subclinical hypothyroidism had elevated triacylglycerides but no alterations in basal metabolic rate or other measured cardiovascular risk factors. ΔTSH was positively associated with Δtriacylglycerides, Δtotal-cholesterol and ΔLDL-cholesterol, independently of age, sex, Δbody mass index and ΔT₄. In the subclinical hypothyroidism group, 92% of individuals normalised their TSH 0.9-2.9 years later.

Conclusions: Children with obesity and subclinical hypothyroidism did not have an altered basal metabolic rate but elevated triacylglycerides. During the follow-up period, TSH changed in parallel with several blood lipids. Elevated TSH often normalised without pharmaceutical intervention within 3 years.

Impact: The present study found that subclinical hypothyroidism in paediatric obesity is related to elevated triglycerides. The present study found that subclinical hypothyroidism is not associated to basal metabolic rate in paediatric obesity. TSH change over time correlated with the change in triglycerides and LDL and total cholesterol. Among subjects with subclinical hypothyroidism at baseline 92% normalised without pharmaceutical intervention within 3 years. This research adds to the knowledge of the longitudinal, natural course of elevated TSH in paediatric obesity which is expected to help to make informed decisions regarding follow-up and evaluation of this patient group.