Racial Differences in Premenopausal Endogenous Hormones

Abstract

Differences in breast cancer incidence across racial groups are well documented. African Americans have the highest rates of premenopausal breast cancer and Asians have lower breast cancer rates across all age groups. We hypothesized that levels of premenopausal endogenous hormones and growth factors, risk factors that have been predictive of breast cancer, would differ by race. Using a cross-sectional study design, we tested this hypothesis in the Nurses' Health Study II. We assayed estradiol, progesterone, prolactin, sex hormone binding globulin (SHBG), insulin-like growth factor-I (IGF-I), and IGFBP-3 in 111 African American and 111 Asian American women, matched to 111 Caucasian women on age, day of luteal phase, and day, time, and fasting status at blood collection. We analyzed the association between race and hormone levels using robust linear regression methods. In multivariate models, compared with Caucasians, African Americans had 18% higher levels of estradiol (P < 0.01), 17% higher free estradiol (P < 0.01), 11% lower SHBG (P = 0.05), 11% higher IGF-I (P < 0.01), 25% higher free IGF-I (P < 0.01), and 9% lower IGFBP-3 (P < 0.01) levels. In multivariate models, compared with Caucasian women, Asian Americans had 22% higher calculated free estradiol (P < 0.01), 31% lower SHBG (P < 0.01), and 25% higher free IGF-I (P < 0.01) levels. No racial differences were found in progesterone and prolactin levels. Our study showed hormone differences consistent with breast cancer risk between Caucasians and African Americans but inconsistent with breast cancer risk between Asian Americans and Caucasians. Further research is needed to explore differences across racial groups and the link between endogenous hormones and breast cancer risk. (Cancer Epidemiol Biomarkers Prev 2005;14(9):2147 -53)

Whites have a more robust hypothalamic–pituitary–adrenal axis response to a psychological stressor than blacks

“…Since there was no difference in prolactin response as there was in HPA axis response between whites and blacks, it would suggest that racial differences do not extend to all neuroendocrine stress responses. Of note, a recent study found no differences in baseline prolactin levels between whites, blacks, and Asian Americans (Pinheiro et al, 2005).…”

Racial disparities in breast cancer outcome

“…In fact, luteal phase estradiol levels are reported to be higher in AA compared with CA women. 54,55 AA women undergo menarche earlier than CA women 56 and also tend to cycle more rapidly than their CA counterparts. 57 Each of these differences in the cycle and its hormones could contribute to outcome differences.…”

Insulin-like growth factor 1 receptor expression in breast cancer tissue and mammographic density

“…Based on this finding, IGF-1R overexpression appears to play an important role in breast cancer patients with dense breast tissue. Based on reports that IGF-1 and IGF-1R expression varies across ethnic groups, ethnicity-based correlations between dense breast tissue and IGF-1R overexpression should be investigated, in order to elucidate the effect of IGF-1R overexpression on breast cancer patients with dense breast tissue (27,28).…”