Effect of thyroxine on initial catch-up growth in children with hypothyroidism

Abstract

Background: Hypothyroidism is a common endocrinal cause of growth retardation in children. Following adequate treatment with thyroxine, growth resumes at an accelerated rate which is known as catch-up growth. There are few observational studies from India on the growth parameters following treatment with thyroxine in children with hypothyroidism.Methods: A retrospective study was done in children aged 2-10 years who were newly diagnosed cases of primary hypothyroidism [Total serum Thyroxine (T4) levels <5 µg/dl and serum Thyroid Stimulating Hormone (TSH) levels ˃15 µU/ml] and treated with oral thyroxine to attain euthyroid state. Height measured before starting treatment and at the time of follow up visits was noted, the Height Standard Deviation Scores (HSDS) were calculated. The effect of thyroxine on linear growth was studied.Results: There were 23 children who were diagnosed as having primary hypothyroidism of whom 16(69.6%) were females and 7(30.4%) were males. The mean age of the children studied was 7.3±2.3 years. The mean dose of thyroxine required to maintain euthyroid status was 4.6±2.2 µg/kg/day. Mean duration of follow up was 13.7±2.4 months. The initial HSDS was - 2.31±0.9 which improved to a final value of - 1.7±0.76 (ΔHSDS0.61, p value <0.0001). Mean height velocity was 8.1 cms/year.Conclusions: Following adequate thyroxine replacement therapy catch-up growth occurs and increased growth velocity leads to partial regain of height deficit in the first couple of years of treatment.