Most cases of endometrial hyperplasia result from high levels of estrogens, combined with insufficient levels of the progesterone-like hormones. This may occur in conditions including obesity, polycystic ovary syndrome, estrogen producing tumours (e.g. granulosa cell tumour) and ceain formulations of estrogen replacement therapy. Endometrial hyperplasia is a significant risk factor for the development or even co-existence of endometrial cancer. Hyper estrogenic state is associated with marked endothelial hyperplasia which regress with progestins.