Cortical and trabecular bone mineral content in women with endometriosis: effect of gonadotropin-releasing hormone agonist and danazol

Cortical bone (distal radius and ulna) and trabecular bone mineral content of the thoracolumbar vertebrae (T-12 to L-4) were measured with single-photon absorptiometry and quantitative computed tomography, respectively, in 55 women with laparoscopically staged endometriosis before, during, and after treatment with a gonadotropin-releasing hormone agonist (GnRH-a) or danazol. Mean pretreatment potassium phosphate mineral contents of T-12 to L-4 were 174 to 201 mg/ml in stage I to IV endometriosis and were within the 100 to 115th percentile of normal women. Similarly, cortical bone mineral contents were normal and were not significantly affected by either medication. Trabecular bone decreased significantly to 92.6 +/- 1.7% (n = 11, P less than 0.001) and 92.3 +/- 2.5% (n = 7, P less than 0.01) of baseline year after 6 months and 9 months of GnRH-a treatment and remained significantly depressed at 95.8 +/- 1.9% (P less than 0.0025) and 94.8 +/- 2.5% (P less than 0.005) 6 months after stopping treatment. Thus, cortical and trabecular bone mineral contents of women with endometriosis are normal, but treatment with GnRH-a induced significant loss of trabecular bone.