20(S)-Hydroxyprogesterone; 20-Hydroxypregn-4-en-3-one; 20α-Dihydroprogesterone; 20α-Hydroxy-4-pregnen-3-one; 20α-Hydroxy-Δ4-pregnen-3-one; 20α-Hydroxydihydroprogesterone; 20α-Hydroxypregn-4-en-3-one; 20α-Hydroxyprogesterone; 20α-Progerol; 4-Pregnen-3-one-20α-ol; NSC 68630; Pregn-4-en-20α-ol-3-one; Pregn-4-ene-20α-ol-3-one; Progesterol-20α; Δ4-Pregnene-20α-ol-3-one;

Δ4-Pregnen-20α-ol-3-one is the main metabolite of Progesterone. Studies shows regulation of estrogen receptor levels in breast cancer by Δ4-Pregnen-20α-ol-3-one and other progesterone metabolites.