Mechanism of Action of Megestrol Acetate in Endometriosis

Molecular Mechanisms

• The American College of Obstetricians and Gynecologists notes that megestrol acetate modifies progesterone receptor expression (PR-A and PR-B ratio), maintaining tissue quiescence 1
• The drug can work through both genomic and non-genomic pathways, providing multiple points of therapeutic intervention 1

Anti-Inflammatory Effects

• The American College of Obstetricians and Gynecologists reports that progestins like megestrol acetate decrease prostaglandin synthesis and infection-mediated cytokine production in endometrial tissues 1, 2
• This anti-inflammatory action counteracts the inflammatory cascade that contributes to endometriosis-related pain 2

Clinical Implications for Reproductive-Age Women

• The American Society for Reproductive Medicine states that megestrol acetate does NOT improve future fertility outcomes and should not be used in women actively seeking pregnancy, with a strength of evidence level of limited or low quality 3