Medroxyprogesterone acetate (MPA, 10–60 mg daily), a 17OH-progesterone derivative available as oral or depot formulation (administered every three months subcutaneously or intramuscularly), is as effective as Gonadotrophin releasing hormone analogs (GnRH agonist) and limited to treat refractory endometriosis due to long-term hypo-estrogenic status, consequently leading to bone loss [176,177]. This evidence concerns the gene GNRH1 and endometriosis.