Reduced Bone Mass in Reproductive-Aged Women with Endometriosis*

Abstract

Cortical and trabecular bone masses were measured by quantitative computed tomography of the distal radius in 41 women (30 +/- 1 yr) with endometriosis documented by laparoscopy and compared to those in 35 normal women (32 +/- 1 yr). Hormonal status was assessed, and a subset of 10 women with endometriosis underwent evaluation of calcium absorption and excretion. Menstrual cycles were regular in all women, and hormonal medication had not been administered during the 3 months before evaluation. Estradiol and progesterone varied as expected with the day of the cycle. Fasting calcium excretion was normal. Mean cortical and trabecular bone mass values in women with endometriosis were compared to those in the normal women. Women with endometriosis had significantly decreased cortical and trabecular bone mass. Cortical bone mass in normal subjects was 1263 +/- 11 Hounsfield units (HU), whereas in endometriosis, cortical bone mass measured 1133 +/- 16 HU (P less than 0.0001). Normal trabecular bone mass was 226 +/- 10 HU compared to a mean trabecular bone mass of 173 +/- 9 HU (P less than 0.0001) in endometriosis. Despite the decrease in bone mass documented by quantitative computed tomography, hormonal and calcium dynamics were normal and, therefore, did not appear to be significant etiological factors in regard to the bone loss. Since immunological abnormalities have been reported in association with endometriosis, immune factors may play a role in the development of bone loss in endometriosis and might be of pathogenic significance in this reproductive disorder.