Racial variation in vitamin D cord blood concentration in white and black male neonates

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

Racial variation in umbilical cord blood sex steroid hormones and the insulin-like growth factor axis in African-American and white female neonates

PURPOSE: To evaluate whether there is racial variation in venous umbilical cord blood concentrations of sex steroid hormones and the insulin-like growth factor (IGF) axis between female African-American and white neonates. METHODS: Maternal and birth characteristics and venous umbilical cord blood samples were collected from 77 African-American and 41 white full-term uncomplicated births at two urban hospitals in 2004 and 2005. Cord blood was measured for testosterone, dehydroespiandrosterone-sulfate, estradiol, and sex steroid hormone-binding globulin (SHBG) by immunoassay. IGF-1, IGF-2, and IGF-binding protein-3 (IGFBP-3) were measured by ELISA. Crude and multivariable-adjusted geometric mean concentrations were computed for the hormones. RESULTS: African-American neonates weighed less at birth (3,228 g vs. 3,424 g, p < 0.004) than whites. Birth weight was positively correlated with IGF-1, IGFBP-3, and the molar ratio of IGF-1 to IGFBP-3, but inversely correlated with the molar ratio of IGF-2 to IGFBP-3. Adjusted models showed higher testosterone (1.82 ng/ml vs. 1.47 ng/ml, p = 0.006) and the molar ratio of testosterone to SHBG (0.42 vs. 0.30, p = 0.03) in African-American compared to white female neonates. IGF-1, IGF-2, and IGFBP-3 were lower in African-American compared to white female neonates, but only the difference for IGF-2 remained significant (496.5 ng/ml vs. 539.2 ng/ml, p = 0.04). CONCLUSION: We provide evidence of racial variation in cord blood testosterone and testosterone to SHBG in African-American compared to white female neonates, and higher IGF-2 in white compared to African-American female neonates. Findings suggest plausible explanations for a prenatal influence on subsequent breast cancer risk and mortality. Further work is needed to confirm these observations