Very low birth weight newborns do not need repeat screening for congenital hypothyroidism

To determine whether repeat screening for congenital hypothyroidism is necessary in newborns weighing <1500 g (very low birth weight [VLBW]).

All VLBW infants born in the province of Québec between October 15, 1993, and October 15, 1994, had a second filter paper sample requested at 6 weeks of age to measure thyrotropin and thyroxine, in addition to these measurements for the routine screening sample. We then conducted a survey of all 4 academic pediatric endocrinology clinics in the province, inquiring about cases of permanent primary congenital hypothyroidism (PPCH) in children born weighing <1500 g or who may have been missed by neonatal screening.

Two specimens were obtained in 465 VLBW newborns. One case of mild transient hyperthyrotropinemia was identified. The survey identified 4 VLBW newborns with PPCH: 1 girl and 1 boy with dyshormonogenesis, 1 athyreotic girl, and 1 girl with thyroid ectopy. All 4 were detected by their initial filter paper specimens. The survey also identified 1 case of PPCH in a girl who had a normal neonatal screen and normal birth weight.

VLBW newborns with PPCH can mount an appropriate thyrotropin response and do not need repeat screening for congenital hypothyroidism.