Cord Serum Thyroid-Stimulating Hormone and Thyroglobulin Levels Decline with Increasing Birth Weight in Newborns*

Abstract Cord serum thyroglobulin (Tg) and TSH levels were related to birth weight in 3 groups of newborn infants composed of 101 infants. Serum free T3 index, free T4 index, and/or T4 also were determined. Group I consisted of normal term newborns (20 females and 19 males), whose mean ± SD gestational ages (40.1 ± 0.7 vs. 40.1 ± 0.5 weeks) did not differ, but whose mean birth weights (3299 ± 282 vs. 3757 ± 447 g) differed significantly (P < 0.005). In female infants, serum Tg levels (r = −0.401; P < 0.05) and the log of TSH levels (r = −0.576; P < 0.005) correlated negatively with birth weight, while Tg levels correlated positively with the log of TSH levels (r = 0.401; P < 0.05). In contrast, none of these correlations was significant for male infants. However, T4 levels and birth weight correlated positively (r = 0.499; P < 0.025) in male infants, but not in female infants. Group II consisted of newborns whose birth weights were less than 2500 g (19 females and 19 males). Mean birth weights of female (...