Ulipristal acetate (UPA) is a selective progesterone receptor modulator (SPRM) used for fibroid treatment. The mechanism underlying its fibroid volume reduction differs from GnRH analogues because:
- A UPA suppresses FSH more potently than LH, reducing estrogen production
- B UPA acts directly on progesterone receptors in myoma cells, inducing apoptosis without inducing hypoestrogenism ✓
- C UPA inhibits aromatase activity within leiomyoma cells
- D UPA acts via anti-glucocorticoid activity to reduce inflammatory mediators in fibroids
Explanation
Ulipristal acetate (UPA) is an SPRM that binds progesterone receptors (PR-A and PR-B) in leiomyoma cells and exerts mixed antagonist-agonist effects. It induces leiomyoma-specific apoptosis and inhibits fibroid cell proliferation directly without causing hypoestrogenism (estrogen levels remain near-normal unlike GnRH analogues). This preserves bone density and avoids menopausal symptoms, which are major drawbacks of GnRH agonists. UPA also directly inhibits the gonadotropin surge (via hypothalamic/pituitary effect) to reduce ovarian production modestly. Fibroid volume reduction of ~36% is seen at 3 months. UPA use was suspended in Europe after reports of serious hepatotoxicity, now subject to restricted access protocols.
Reference: Shaw's Textbook of Gynaecology, 17th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.