Current hypotheses include a link between obesity and elevated oestrogen levels, inflammation, type 2 diabetes and hyperinsulinaemia.9 In recently published studies, we found altered expression of genes involved in insulin signalling (IGF‐1, IGFBP1 and PTEN) and lipogenic gene regulation in the endometrium and serum of women with PCOS and EC compared with controls.10, 11 Genes related to immunoregulation/inflammation,12 antioxidants9 and impaired progesterone‐mediated decidualization13 have also been suggested as possible mechanisms linking PCOS and EC. The gene discussed is INS; the disease is type 2 diabetes mellitus.