Pharma & Specialty Chemical Standards

Ethisterone, IUPAC name 17α-Ethynyl-17β-hydroxy-18-methyl-5-pregnene-3,20-dione (C20H26O2, molecular weight 298.42 g/mol), is a synthetic 19-norandrogenic steroid. Structurally, it features an ethynyl group at C17α, a hydroxyl at C17β, and a methyl group at C18, conferring progestogenic and androgenic activity. Therapeutically, it was historically used in hormonal contraceptives and for endometriosis. It is a white crystalline solid with low water solubility (logP ~3.2) and a melting point of ~160–165°C. Mechanistically, it binds to progesterone receptors, modulating gene expression, and exhibits androgenic effects via androgen receptor interaction, though its clinical use has diminished due to side effect profiles.