5a-Pregnane-3,20-dione (5alphaP, 5-a-dihydroprogesterone, 3,20-allopregnanedione, 5-Alpha-Dihydro Progesterone) is the endogenous progesterone metabolite. 5a-Pregnane-3,20-dione depolymerizes actin and decreases expression of actin and vinculin. 5a-Pregnane-3,20-dione is involved in promoting breast neoplasia and metastasis by affecting adhesion and cytoskeletal molecules.