Growth hormone (GH) released from the pituitary gland stimulates production and release of IGF-1 from the liver, and elevated levels of circulating GH leads to insulin resistance and hyperinsulinemia.11,12 Although there is no evidence linking circulating GH levels with breast cancer risk,13,14 other lines of research suggest a role of the GH signaling pathway in breast cancer. This evidence concerns the gene GH1 and hyperinsulinism.