 Certain other progestins are also active in this assay, whereas progesterone acts neutrally.It is unclear if these findings may explain the different risks of breast cancer observed with progesterone, dydrogesterone, and other progestins such as medroxyprogesterone acetate and norethisterone in clinical studies.Dydrogesterone and its major metabolite, 20α-DHD, have predictable pharmacokinetics.