Thyroid function tests in newborns of mothers with hypothyroidism

Area of Science:

• Neonatal Medicine
• Endocrinology
• Public Health Screening

Background:

• Maternal hypothyroidism necessitates careful monitoring of newborns.
• Current practice often includes both newborn screening and repeat thyroid function tests (TFT) at two weeks for these infants.
• The added value of repeat TFT beyond newborn screening is debated.

Purpose of the Study:

• To evaluate the clinical benefit of routine thyroid function tests (TFT) at two weeks of age in neonates born to mothers with hypothyroidism.
• To compare the efficacy of repeat TFT with the national newborn screening program in detecting congenital hypothyroidism.

Main Methods:

• Retrospective study of 1392 neonates born to mothers with hypothyroidism between 2010-2016.
• Data collected from hospital records, community clinics, and Israel's national newborn screening program.
• Comparison of results from newborn screening tests and serum TFT performed at least two weeks after birth.

Main Results:

• Eight cases of congenital hypothyroidism were detected by both newborn screening and the two-week TFT.
• No neonates had a normal newborn screening result followed by an abnormal two-week TFT.
• The two-week TFT identified no additional cases not already identified by the initial newborn screening.

Conclusions:

• Performing thyroid function tests at two weeks of age provides no added clinical benefit for neonates born to mothers with hypothyroidism, beyond the established newborn screening program.
• The current newborn screening program is sufficient for identifying congenital hypothyroidism in this at-risk population.