Use of GnRH antagonists in the treatment of endometriosis.

Endometriosis is an oestrogen-dependent disease that is treatable by oestrogen withdrawal, a therapy that has been effectively provided by the use of a gonadotrophin-releasing hormone (GnRH) agonist. Complete oestrogen withdrawal results in unacceptable side-effects, in particular in accelerated bone density loss. This problem has been effectively overcome with 'add-back therapy' using low-dose oestrogens and progestins in combination with a GnRH agonist to limit these side-effects, while still allowing regression of endometriotic lesions. The aim of this study was to determine the feasibility of using a subcutaneous injection of GnRH antagonist in the treatment of endometriosis. All patients (15/15; 100%) reported a symptom-free period during GnRH antagonist treatment, including mood changes, hot flushes, loss of libido, vaginal dryness and other symptoms. Serum oestradiol oscillated around a mean concentration of 50 pg/ml during therapy. Diagnostic laparoscopy before GnRH antagonist administration showed a mean stage III of disease. Regression occurred in 60% of cases (9/15) and the degree of endometriosis declined to stage II. Sequential administration of the GnRH antagonist cetrorelix (Cetrotide) in a 3 mg dosage once weekly over 8 weeks creates a new opportunity for medical treatment of symptomatic endometriosis. Preserving basic oestrogen production during the course of treatment apparently does not influence regression of disease, and has no major side-effects.