Racial variation in sex steroid hormones and the insulin-like growth factor axis in umbilical cord blood of male neonates.

BACKGROUND: To address whether umbilical cord blood concentrations of sex steroid hormones and the insulin-like growth factor (IGF) axis differ between African-American and White male neonates.
METHODS: In 2004 and 2005, venous cord blood samples were collected from 75 African-American and 38 White male full-term uncomplicated births along with birth weight, placental weight, mother's age and parity, and time of birth. Testosterone, androstanediol glucuronide, estradiol, and sex hormone binding globulin (SHBG) were measured by immunoassay, and IGF-I, IGF-2, and IGF binding protein (BP)-3 by ELISA. Crude and multivariable-adjusted geometric mean concentrations were computed.
RESULTS: Androstanediol glucuronide, estradiol, and SHBG concentrations did not differ by race; however, the molar ratio of testosterone to SHBG was higher in African-American than White male babies after adjustment (P = 0.01). Both before and after adjustment, Whites had higher concentrations of IGF-I (adjusted; White, African-American, 93.1, 71.9 ng/mL), IGF-2 (537.3-474.8 ng/mL), and IGFBP-3 (1,673-1,482 ng/mL) than African-Americans (P < 0.05), although the molar ratio of IGF-I plus IGF-2 to IGFBP-3 did not differ by race.
CONCLUSION: The higher cord blood testosterone to SHBG ratio in African-American compared with White male babies after taking into account maternal and birth factors is compatible with the hypothesis that differences in androgen levels in utero contribute to their higher prostate cancer risk, although we would have expected crude differences as well. Lower cord blood IGF-I and IGF-2 levels in African-American compared with White male babies are not consistent with the hypothesis that differences in growth factor levels contribute to their higher prostate cancer risk.