Screening in specific categories of neonates exposed to congenital hypothyroidism

Prenatal and postnatal thyroid function disorders in preterm neonates lead to disturbances in the maturation of nerve tissue, skeleton, and other tissues of the organism. Abnormalities caused by thyroid hormone deficiency in this period lead to irreversible changes that do not disappear even after subsequent thyroid compensation. In the present screening program, TSH was determined on day 3–5 of life, followed by an assay after the 3rd week of life in preterm neonates. In this period, TSH values are often low, as the immature hypothalamic-pituitary system secretes insufficient amounts of TSH, even when fT4 and FT3 are reduced. Given the need for early diagnosis and treatment of primary and secondary hypothyroidism in premature infants and children with low birth weight (small for gestational age- SGA), determination of TSH and fT4 on day 3-5 of life in premature infants and SGA children is recommended, irrespective of the screening, in order to include l-thyroxine treatment of secondary or primary hypothyroidism before the end of the second week of life.