ESPE Abstracts

Background: Neonatal thyroid stimulating hormone (TSH) is influenced by several factors. But the effects are not consistent but different depending on subjects and kind of blood sample.

Objective and hypotheses: This study was to evaluate the effect of neonatal, maternal, and delivery factors on neonatal TSH of healthy newborns.

Method: Medical records of 713 healthy infants born through normal vaginal delivery were reviewed. TSH level obtained by neonatal screening test was analyzed according to the difference of neonatal, delivery, and maternal factors. The relationships between neonatal TSH and free T4 and 17 α-hydroxyprogesterone (17 OHP) were also evaluated.

Results: Sex, birth weight, and gestational age were not associated with neonatal TSH. Twin babies and neonates born through vacuum extraction had higher TSH levels than controls. There was a significant negative association between TSH level and time interval between birth and newborn screening test. First babies had higher TSH levels than babies of higher birth order. Duration of membrane rupture, Apgar scores and induction times did not influence TSH level. There was no difference in TSH level according to maternal disease such as diabetes, pregnancy induced hypertension, and thyroid disease, nor maternal medication such as insulin, steroid, and thyroid hormone. Neonatal TSH level was not associated with free T4 level but had a positive relationship with 17OHP level. Multiple linear regression analysis also showed that time interval from birth to test, twin baby, birth order, and vacuum assisted delivery influence on neonatal TSH level.

Conclusion: Neonatal TSH level of healthy normal newborns is related with multiple factors. Acute stress during delivery rather than feedback mechanism of thyroxine may influence the neonatal TSH level in early neonatal period.