A synthetic progestin; binds to the progesterone receptor (EC50 = 50.3 nM); increases uterine weight in rabbits (ED50 = ~ 1 μg), maintains pregnancy in 40-50% of rats at 0.03-0.1 mg per day, and completely inhibits spontaneous ovulation in rats at 10 μg per day; increases cell proliferation in the adult female mouse brain, increasing the production of new neurons and oligodendrocytes, at 8 μg, i.c.v, via osmotic minipump for four weeks