Determinants of levothyroxine dose required to achieve euthyroidism in pediatric population-a hospital-based prospective follow-up study.

We analyzed the relation of pretreatment anthropometric measures and serum thyrotropin (TSH) with the levothyroxine requirement. Children (3-18 years) brought to endocrine clinic with newly diagnosed acquired primary hypothyroidism were enrolled consecutively and prospectively with follow-up (July 2014 to April 2016). Children were started on levothyroxine, and dose was adjusted at regular intervals until achieved euthyroidism (serum TSH 0.4 to 4.5 mIU/L). The relationship of age, gender, height, weight, and serum TSH with levothyroxine dose was analyzed by univariate and multivariate regression analysis. Data of 51 children (42 girls and 9 boys) was used for the analysis. Age, weight, height, and serum TSH had significant correlation with levothyroxine daily dose based on weight (D/W) and dose based on BSA (D/BSA). Log10 TSH and gender explained ∼60% absolute levothyroxine daily requirement. The final model built with height and serum TSH predicted ∼85% of D/W and ∼80% of D/BSA.

CONCLUSION: Pretreatment height and serum TSH can be used to determine levothyroxine dose needed to achieve euthyroidism in a newly diagnosed acquired primary hypothyroidism in children. What is Known: • The starting dose of levothyroxine is currently recommended based on the age of children. What is New: • In pediatric population, the effect of age on levothyroxine daily dose requirements can be explained by pretreatment height. • Pretreatment serum TSH level is an important predictor of levothyroxine daily dose in children with newly diagnosed primary hypothyroidism.