Levothyroxine supplementation for obesity-associated thyroid dysfunction in children: a prospective, randomized, case control study

Introduction
The specific treatment of thyroid dysfunction associated with simple obesity (SO) in children is controversial.

Material and methods
Fifty-one children having SO (BMI ≥ 2 Z-score) aged 6–12 years with elevation of serum thyroid stimulating hormone (TSH) (4–10 mIU/l) with or without alterations in serum triiodothyronine (T3) or thyroxine (T4) were randomised to receive either routine weight management intervention (group 1, n = 25) or additional low dose levothyroxine (~0.5 µg/kg/day) (group 2, n = 26) and followed up at 3-month intervals for 6 months.

Results
The mean BMI Z-scores decreased in both groups from baseline to 3 and 6-month time points (group 1, 3.69 ±1.31 to 3.24 ±1.45 to 2.84 ±1.46, p = 0.03 and group 2, 4.31 ±2.11 to 4.08 ±1.92 to 3.50 ±1.93, p = 0.02). However, the decrease was similar in the 2 groups (–0.80 ±0.77 vs –0.97 ±0.69, p = 0.19). All children had isolated hyperthyrotropinemia. The mean TSH levels decreased from baseline to endpoint in group 1 (5.51 ±1.0 to 4.14 ±1.0 to 4.04 ±1.1 mIU/l, mean change –1.44 ±1.20, p = 0.001) and in group 2 (5.89 ±1.10 to 5.89 ±1.10 to 3.89 ±1.48 mIU/l, mean change –1.93 ±1.15, p = 0.001). The decrease in TSH levels was also similar in the 2 groups (p = 0.69). TSH normalized in 48% and 57.6% in group 1 and group 2 respectively. The decrease in total cholesterol and triglyc-erides was also similar in the 2 groups.

Conclusions
Addition of levothyroxine to weight management interventions has no beneficial effect on BMI reduction as well as parameters of lipid and thyroid profiles, and should not be prescribed to children with obesity associated thyroid dysfunction.