9β,10α,17α-pregna-4,6-diene-3,20-dione ((8S,9R,10S,13S,14S,17R)-17-Acetyl-10,13-dimethyl-8,9,10,11,12,13,14,15,16,17-decahydro-1H-cyclopenta[a]phenanthren-3(2H)-one) is an isomer of Dydrogesterone, a synthetic progestin largely used in hormone therapy, on the central nervous system by studying two markers of the neuroendocrine function. 9β,10α,17α-pregna-4,6-diene-3,20-dione is one of major impurities of dydrogesterone. The physiological and toxicological properties of this compound have not been evaluated in humans.