This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Which of the following factors causes endometrial hyperplasia? 
Select and explain. 
A. Estrogen, B. Danazole, C. Perimenopausal age, D. None of the above
A: Estrogen
Answer: A: Estrogen 
Explanation: 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.