Effect of 2 Years of Treatment with Levothyroxine on Cardiovascular Risk Factors in Children with Mild Idiopathic Subclinical Hypothyroidism

Background: The benefits of levothyroxine (L-T4 ) therapy in subjects with mild SH (TSH between 5 and 10 mU/l with normal FT4 values) are controversial. Current recommendations in adults suggest to start on treatment selected groups of subjects with mild SH and evidence of atherosclerotic CV disease. Data in children are lacking. Objective and hypotheses: To investigate the effect of L-T4 treatment on CV risk factors in children with mild idiopathic SH. Method: Thirty-nine children (19 males) aged 9.32G0.65 years with long-lasting idiopathic SH underwent waist circumference, lipid profile, homocysteine (Hcy) and asymmetric dimethylarginine (ADMA) measurements. Non-HDL-C and atherogenic index (AI) were also calculated. Waist to height ratio (WHtR) was used as indicator of visceral adiposity. Thirtynine euthyroid children were enrolled as controls. Results: At baseline SH subjects compared to controls showed significantly higher WHtR (0.54G0.01 vs 0.49G0.01; PZ0.0072), ADMA (0.99G0.02 vs 0.90G0.02 mmol/l; PZ0.002), LDL-C (92.06G3.65 vs 75.05G5.76 mg/dl; PZ0.0148), non-HDL-C (106.41G4.05 vs 86.44G6.49 mg/dl; PZ0.0109), AI (3.18G0.14 vs 2.75G0.12; PZ0.0232) and Hcy levels (9.34G0.41 vs 7.71G0.32 mmol/l; PZ0.0024) and significantly lower HDL-C concentrations (52.30G1.79 vs 61.06G2.32 mg/dl; PZ0.0038). After 2-years of L-T4 therapy SH subjects had a significant reduction in WHtR (0.54G0.01 vs 0.50G0.01; PZ0.0414) and ADMA concentrations (0.99G0.02 vs 0.38G0.06 mmol/l; P!0.0001). Lipid profile and Hcy levels became comparable to controls, although the changes from baseline values did not reach a statistical significance.Conclusion: L-T4 treatment in children with mild idiopathic SH is associated with a trend toward improvement of the subtle metabolic abnormalities in visceral adiposity, lipid profile, Hcy and ADMA levels observed in untreated children. Our data suggest the CV risk profile should be taken into account in the decision to treat or not a child with asymptomatic mild SH.