 Similarly, like oral progesterone but in contrast to other progestins, dydrogesterone does not appear to further increase the risk of venous thromboembolism when used in combination with an oral estrogen.Dydrogesterone may also provide inferior endometrial protection relative to other progestins such as medroxyprogesterone acetate and norethisterone acetate, with a significantly increased risk of endometrial cancer in combination with an estrogen with long-term therapy (>5 years).Dydrogesterone weakly stimulates the proliferation of MCF-7 breast cancer cells "in vitro", an action that is independent of the classical PRs and is instead mediated via the progesterone receptor membrane component-1 (PGRMC1).