Effect of gonadotropin-releasing hormone agonist on the bone mineral density of patients with endometriosis.
OBJECTIVE: To examine changes in bone mineral density (BMD) of patients treated with GnRH agonist (GnRH-a) by dual-energy X-ray absorptiometry and to understand factors related to bone loss. DESIGN: Prospective controlled trial examining BMD during and after GnRH-a therapy every 24 weeks for 18 months in patients with endometriosis compared with nontreated controls. SETTING: Outpatients clinic at a university hospital and its affiliated outpatient clinic. PATIENTS: Twenty-two patients with endometriosis as GnRH-a-treated group, 12 healthy women with normal menstrual cycle, and 7 patients with mild endometriosis as control group. INTERVENTIONS: Patients were treated with a GnRH-a (buserelin acetate) at 900 micrograms/d by nasal spray for 24 weeks. RESULTS: The significance of differences in change-rates at all measured points in both groups was assessed by analysis of variance. The interaction between treatment and period was significant, and only week 24 of the GnRH-a-treated group was significantly lower compared with baseline. The reduction rate of BMD was high in patients 33 years of age or younger compared with those who were 34 years of age or older. According to a multiple-regression model, the most important factor related to bone loss was the post-treatment serum levels of E2. CONCLUSION: At the end of treatment, BMD was significantly lower than that of the control group, and the reduction rate was 3.4%. A factor related to bone loss was degree of ovarian suppression.