Racial variation in steroid hormone and growth factor concentration: US African-American and white female newborns

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Purpose: Sex steroid hormones and the insulin-like growth factor-axis are associated with risk of female breast cancer. Whether the hormonal and growth factor milieu in utero may also contribute to adult breast cancer and explain the higher breast cancer incidence and mortality rates in younger African-American women is unknown. Thus, we evaluated variation in venous umbilical cord blood concentrations of sex steroid hormones and components of the IGF-axis between female African-American and white newborns.
 >Methods: Data were collected from 118 women who gave birth at two urban hospitals in Maryland. At the time of delivery, cord blood was collected from 77 African-American and 41 white full-term, uncomplicated births, along with mother’s age, placental weight, baby’s weight, parity-live births, birth season and time of birth. Cord blood was assayed for testosterone, dehydroepiandrosterone (DHEAS), estradiol, sex-steroid hormone binding globulin (SHBG), insulin-like growth factor (IGF)-1, IGF-2, and IGF binding protein-3 (IGFBP-3). Geometric mean concentrations were compared without and with adjustment for birth weight, placental weight, mother’s age and parity, and time of day of birth.
 >Results: White mothers were older (28.1 vs. 24.1 yr, p<0.05) and delivered babies with higher birth weights (3424 vs. 3228 g, p<0.05) when compared to African-American mothers. When examining crude geometric means, cord blood concentrations of testosterone, DHEAS, and estradiol did not differ by race, although the molar ratio of testosterone to SHBG was possibly higher in African-American compared to white female babies (p=0.06). After multivariable adjustment, both the concentration of testosterone (p=0.04) and the molar ratio of testosterone to SHBG (p=0.04) were statistically significantly higher in African-American compared to white female babies. When examining crude geometric means, cord blood concentrations of IGF-1, IGF-2, and IGFBP-3 were significantly higher in white compared to African-American female babies. After multivariable adjustment, these concentrations were still higher in whites compared to African-Americans, but only the difference for IGF-2 remained significant.
 >Conclusion: We provide evidence of racial variation in sex steroid hormones and components of the IGF-axis in the in utero environment. Further work is needed to determine whether these observations may explain the racial disparity in breast cancer incidence and mortality in the US.
 >Funded by: National Cancer Institute U54 CA091409 and CA091431.