thyroxine and thyrotropin levels in cord blood sera from south of iran

birth is associated with significant changes in the hypothalamic-pituitarythyroid axis and these changes complicate the proper assessment of thyroid function in neonates. normal values fort4 (thyroxine) and tsh (thyroid stimulating hormone) in cord blood are not well established. the present study was carried out on 4000 specimens of cord sera of both sexes in order to establish reliable reference values for these hormones. our data imply that the level oft4 in cord sera (mean± 1 sd: 10.99±2.46 µg/dl) is less than that of the neonatal period but is comparable to that of older infants. the concentration of tsh (mean±1 sd: 7.09+4.54µu/ml) is comparable to the level expected in the first week of life but is higher than that of older infants. the values of t4 and tsh obtained from cord blood of boys and girls did not show any statistically significant differences. it is suggested that these values can be used as normal reference values for t4 and tsh in cord blood.