Frequency of thyroid status monitoring in the first year of life and predictors for more frequent monitoring in infants with congenital hypothyroidism.

Abstract

The essential role of thyroid hormones for normal brain development during a critical period of life is well established. Neonatal screening programs for congenital hypothyroidism (CH) enable early detection of patients and attainment of euthyroid status as quickly as possible. Adequate and accurate monitoring of thyroid function is necessary. In the study we aimed to determine the periodicity of thyroid function testing in the first year of life (3-month intervals versus <3-month intervals monitoring). We retrospectively analyzed charts of CH children from Macedonia detected on neonatal screening during a 3-year period (2011-2014). Needs for monthly thyroid monitoring were defined according to the recommendations: a dose change within a month of a previous control, values of T4/FT4 not in the upper half of the reference range, and a high or very low thyroid-stimulating hormone (TSH) value. Monthly thyroid testing was indicated in more than a third of CH patients during the first year of life. Children who needed more frequent monitoring intervals had a higher initial value of TSH (p=0.032) and a lower value of T4 (p=0.038) than those requiring less frequent monitoring. The sex, birth weight, age of treatment onset, initial L-thyroxine dose, and L-thyroxine dose at 1-year of age in our study were not predictive factors for more frequent thyroid monitoring. Children with severe hypothyroidism at birth are potential candidates for more frequent thyroid monitoring during the first year of life, although the individual patient approach should not be avoided as variations in TSH values are very common.