Evaluation of Thyrotropin and Thyroxine Levels in The First Month of Life

Özet

BACKGROUND/AIMS Thyrotropin (TSH) and thyroxine (FT4) levels in neonates are not similar to those in older children and adults. The aim of this study is to determine the TSH and FT4 hormone levels in newborns aged >37 gestational weeks. MATERIAL and METHODS The blood samples for TSH and FT4 obtained from newborns aged >37 gestational weeks were analyzed at postnatal 4-7, 8-14, 15-21, and 22-30 days and established as reference intervals for the first week of life, in addition to the mean and median levels for other observation points. RESULTS There was no significant difference according to gender, gestational age, and mode of delivery (p>0.05); therefore, a pooled analysis was performed. The lower and upper limits of the TSH and FT4 levels from the 4th to 7th day of life were 1.20-10.70 mIU/mL and 0.87-2.20 ng/dL, respectively. CONCLUSION We demonstrated that the TSH and FT4 levels change during the neonatal period without a significant sex difference.