Maternal and cord blood hormone levels in the United States and China and the intrauterine origin of breast cancer.

Background: Breast cancer is less common in China than in the United States and perinatal characteristics predict breast cancer risk in the offspring. We determined levels of pregnancy hormones in Boston and Shanghai to identify those possibly involved in the intrauterine origin of breast cancer.
Participants and Methods: We compared maternal and cord blood levels of estradiol, estriol, testosterone, progesterone, prolactin, insulin-like growth factors (IGF) 1 and 2, insulin-like growth factor-binding protein 3, adiponectin and sex hormone-binding globulin (SHBG) in 241 Caucasian and 295 Chinese women.
Results: In both centers, hormone levels at the 16th were predictive of those at the 27th gestational week, but there was little correlation between maternal and cord blood levels. In cord blood, we found significantly (P < 0.01) higher levels of estradiol (44.2%), testosterone (54.5%), IGF-2 (22.7%) and strikingly SHBG (104.6%) in Shanghai women, whereas the opposite was true for IGF-1 (-36.8%).
Conclusions: Taking into account the current understanding of the plausible biological role of the examined endocrine factors, those likely to be involved in the intrauterine origin of breast cancer are SHBG and IGF-2, with higher cord blood levels among Chinese, and IGF-1, with higher cord blood levels among Caucasian women.