Surgically induced endometriosis attenuates accrual of bone mineral density in growing rats

OBJECTIVE: A possible association of endometriosis with decreased bone mineral density in women has been proposed. It has been reported that cortical and trabecular bone mass of the distal portion of the radius is decreased in patients with endometriosis. The objective of this study was to investigate the relationship between endometriosis and bone mineral density with the use of a rat model. STUDY DESIGN: Cycling female Sprague-Dawley rats (180 days old) were randomly assigned to 1 of 2 groups. The treatment group (n = 16) underwent surgical induction of endometriosis. Female rats (n = 17) with surgically transplanted abdominal muscle served as control animals. Dual-energy x-ray absorptiometry measurements were obtained before surgery and after 90 days with a Lunar DPX-MD+ (GE Lunar, GE Medical Systems, Milwaukee, Wis) bone densitometer, with software standardized for small animal research. RESULTS: Experimental animals had grossly visible endometriotic disease at necropsy (90 days). The mean net change in total bone mineral density from baseline to 90 days in the control group was +0.019 +/- 0.002 g/cm2, whereas the mean net change in total bone mineral density for the experimental group was +0.013 +/- 0.002 g/cm2. The experimental group gained less bone than the control group (P = .02). CONCLUSION: The age-appropriate increase in bone mineral density known to occur in this animal model is attenuated by surgically induced endometriosis. This finding supports the idea that endometriosis might be associated with decreased bone mineral density.