Screening for congenital hypothyroidism: the value of retesting after four weeks in neonates with low and very low birth weight

Abstract

Objectives Thyroid-stimulating hormone (TSH), normally a reliable screening test for congenital hypothyroidism (CH), may fail to detect cases among infants who have low and very low birth weight. The purpose of this study was to identify neonates with false-negative screening results. Setting A province in Poland in which 3854 neonates had body weight p2500 g, between 1999 and 2001. Methods TSH levels in blood on filter paper were measured in all neonates between the third and sixth days after birth, but were repeated in low and very low birth weight infants after four weeks of age.Results The repeat test showed TSH levels X10 mIU/L in 19 of the 3854 low birth weight neonates. The final diagnosis in these neonates was permanent CH in two, transient CH in five, possible compensated CH in six and transient high TSH in six. Of the 19, 16 (84%) required iodine and/or thyroxine replacement therapy. Conclusions In neonates with low and very low birth weight, normal TSH levels measured between the third and sixth day of life do not exclude thyroid dysfunction, but a repeat TSH measurement after the fourth week of life identifies the false-negative results. In our data, the prevalence of primary and secondary hypothyroidism (both permanent and transient) was about 0.5%.

Hipotireoidismo congênito: recomendações do Departamento de Tireoide da Sociedade Brasileira de Endocrinologia e Metabologia

“…Late TSH elevations are particularly common in children with low birth weight (< 2,500 g) and in preterm births (39) …”

Update on the Management of Congenital Hypothyroidism

“…The etiologies include thyroid dysgenesis (aplasia, hypoplasia, ectopy), thyroid dyshormonogenesis, hypothalamic-pituitary (TSH) deficiency (if T 4 is also measured) and transient hypothyroidism, usually iodine-, drug- or maternal antibody-induced (table 1). Several modifications of CH screening programs have been introduced to improve detection of infants with delayed increase in serum TSH and with central hypothyroidism [5,6,7]. Repeated testing at 2–6 weeks of age detects an additional 10% of infants with CH and the addition of T 4 measurement detects another 12–15% of infants with central hypothyroidism; some 80% of these cases manifest multiple pituitary hormone deficiencies [6,7].…”

Comparison of One-Tier and Two-Tier Newborn Screening Metrics for Congenital Adrenal Hyperplasia

“…If the screen was positive for CAH, it was automatically sent for second-tier screening. The purpose of the NICU 3-screen system was to capture premature infants with initial FN newborn screens for congenital hypothyroidism due to delayed thyrotropin elevations 11,12. Because Minnesota' s NBS Program does not differentiate repeat screens, all analytes, not just thyrotropin, were also screened 3 times, including 17OHP.…”