A synthetic form of the endogenous hormone progesterone. Progesterone binds to the progesterone receptor, resulting in dissociation of heat shock proteins, receptor phosphorylation, and transcription activation through direct or indirect interaction with transcription factors. This agent exerts inhibitory effects on estrogens by decreasing the number of estrogen receptors and increasing its metabolism to inactive metabolites. Progesterone induces secretory changes in the endometrium, decreases uterine contractility during pregnancy, and maintains pregnancy. Check for active clinical trialsusing this agent.