Risk of progression from endometrial hyperplasia to carcinoma is significant; up to 40% of women suffering from endometrial hyperplasia with atypia go on to develop carcinoma, the most common fatal gynaecological malignancy.21 This rate is expected to increase by up to 100% globally over the next 20 years.22 The biguanide insulin sensitiser metformin has been linked to reversal of endometrial hyperplasia18 and, if it can be used in this way, may contribute to decreasing the prevalence of endometrial carcinoma without leading to the fertility consequences of current therapies. Here, INS is linked to carcinoma.