GH1 and cancer: Reduced susceptibility to carcinogenesis of molecularly reprogrammed mammary cells is hypothesized to explain the long-term beneficial effect of pregnancy.19 Conversely, highly elevated growth hormones, primarily estrogens, could explain the initiation of carcinogenic changes in epithelial tissue, or progression of already established cancer.20 We were interested in exploring whether maternal estrogen metabolite concentrations played a role in this elevated risk.