Growth development in children with congenital hypothyroidism: the effect of screening and treatment variables—a comprehensive longitudinal study

Investigating the screening and early treatment factors potentially affects the growth status of the patients with congenital hypothyroidism. In a longitudinal study, 760 (45 % girl) neonates born in 2002–2009 with congenital hypothyroidism diagnosed by neonatal screening in Isfahan–Iran were followed up to 5 years from the time of diagnosis (i.e., 3–4 records for the first year of age and 2–3 records after that). During follow-up, height, weight, and head circumferences of the patients were measured. Diagnostic and therapeutic factors included serum thyroxine and thyroid stimulating hormone concentration at diagnosis and after treatment initiation, the age at onset of treatment, the first therapeutic dosage, and age at first normalization of thyroxine and thyroid stimulating hormone. Quantile regression for longitudinal data was used for determining the effects of main factors on growth development. Longitudinal growth in height and weight was significantly correlated with the age at onset of treatment and the first therapeutic dosage (p < 0.01), while head circumference only with first therapeutic dosage (p < 0.05). Growth in weight and head circumference was affected by thyroid stimulating hormone at the time of diagnosis (p < 0.05). Also the age of thyroxine normalization had heterogeneous significant impact over the proposed quantiles on weight (p < 0.05), height (p < 0.01), and head circumference (p < 0.001). Among studied factors, the first therapeutic dosage, age at onset of treatment and age of thyroxine normalization seem to be more important for anthropometric development, suggesting that more optimal outcome might be achievable through earlier treatment and appropriate levothyroxine dosage.