Aim: The aim of this study is to evaluate racial variation in umbilical cord blood concentration of vitamin D and to explore its correlation with markers of the insulin-like growth factor axis (IGFs) and sex steroid hormones in white and black male neonates.
Methods: In 2004-2005, venous umbilical cord blood samples were collected from 75 black and 38 white male neonates, along with maternal and birth characteristics from two hospitals in Maryland, United States. 25-Hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)(2)D] were measured by radioimmunoassay and testosterone, estradiol, and sex hormone-binding globulin (SHBG) by immunoassay and IGF-1, IGF-2, and IGF-binding protein-3 by ELISA. Crude and multivariable-adjusted geometric mean concentrations were computed.
Results: Mean 25(OH)D levels were lower in black than in white neonates (11.44; 95 % CI 10.10-12.95 ng/mL vs. 18.24; 95 % CI 15.32-21.72 ng/mL; p < 0.0001). Black neonates were at higher risk of suboptimal vitamin D levels [25(OH)D < 20 ng/mL] than whites (84 vs. 63 %). 25(OH)D concentrations varied by season in whites but not in blacks and were significantly inversely correlated with mother's parity (number of live births) in blacks but not in whites. Mean concentration of 1,25(OH)(2)D did not differ by race. 25(OH)D and 1,25(OH)(2)D did not correlate with IGFs, sex steroid hormones, and SHBG.
Conclusions: Suboptimal vitamin D levels were prevalent especially in blacks and influenced by mother's parity and by season. The observed vitamin D differences between black and white neonates warrant further evaluation of the etiology of the disparity in chronic diseases in adulthood.