text: Progesterone also appears to be involved in the pathophysiology of breast cancer, though its role, and whether it is a promoter or inhibitor of breast cancer risk, has not been fully elucidated. Most progestins, or synthetic progestogens, like medroxyprogesterone acetate, have been found to increase the risk of breast cancer in postmenopausal women in combination with estrogen as a component of menopausal hormone therapy. The combination of natural oral progesterone or the atypical progestin dydrogesterone with estrogen has been associated with less risk of breast cancer than progestins plus estrogen. However, this may simply be an artifact of the low progesterone levels produced with oral progesterone. More research is needed on the role of progesterone in breast cancer.