Neonatal Thyroid Stimulating Hormone # (TSH)

Normal TSH in newborns is higher than in older children. A postnatal surge can raise TSH transiently (often up to about 60 mIU/L); by 48–72 hours many screening programs use cutoffs around 10–20 mIU/L. By two weeks of age TSH usually falls to below roughly 10 mIU/L. Persistent values above screening cutoffs require prompt clinical follow-up.

High neonatal TSH usually reflects congenital hypothyroidism from thyroid dysgenesis (agenesis, ectopy, hypoplasia) or dyshormonogenesis (hormone‑synthesis defects). Other causes include maternal factors (antithyroid drugs, TSH‑receptor blocking antibodies), iodine deficiency or excess, prematurity or severe illness, and transient hypothyroidism from perinatal iodine exposure or stress. Early screening distinguishes permanent from transient elevations.

A TSH test in newborns screens for congenital hypothyroidism, a condition where the baby’s thyroid doesn’t make enough hormone. Early detection—usually by heel‑prick in the first days of life—allows prompt treatment with thyroid hormone replacement to prevent growth failure, poor motor development and irreversible intellectual disability. Routine screening ensures timely diagnosis even when signs are subtle or absent.

Normal TSH is roughly 0.4–4.0 mIU/L. Alarming levels are generally TSH <0.1 mIU/L (marked hyperthyroidism risk) or >10 mIU/L (significant hypothyroidism risk). These values increase risk of cardiovascular, metabolic or developmental problems and commonly prompt treatment. Contact your clinician promptly if your TSH is in these ranges, if you have strong symptoms, or if you are pregnant.

Yes. Elevated TSH (reflecting hypothyroidism) during pregnancy or in newborns can harm babies: maternal hypothyroidism raises risks of miscarriage, preterm birth, low birth weight and impaired fetal brain development. In infants, untreated high TSH/congenital hypothyroidism can cause poor growth and neurodevelopmental delay. Early screening and prompt levothyroxine treatment greatly reduce these risks.

High TSH in a newborn suggests congenital hypothyroidism. Immediate steps: confirm with repeat TSH and free T4, start levothyroxine promptly (typically 10–15 µg/kg/day) under pediatric endocrinology, and monitor TSH/free T4 frequently with dose adjustment. Give medication consistently on an empty stomach (tablet can be crushed in a little water/breast milk), avoid iron/calcium/soy at dosing, and ensure long-term follow-up.