Osteoporosis in anorexia nervosa: the influence of peak bone density, bone loss, oral contraceptive use, and exercise.

ABSTRACT

PIP: In Australia, a group of 65 patients with anorexia nervosa were studied. The diagnosis was based on DSM-III-R criteria. A total of 12 patients had primary amenorrhea. Of the 53 patients with secondary amenorrhea, 16 had taken oral contraceptives during a illness. A total of 19 patients were exercisers. 52 premenopausal healthy women volunteers with no illnesses known to affect bone were studied as the control group. Total-body and regional bone density (lumbar spine, L2-4, femoral neck, Ward's triangle, and intertrochanteric regions) were measured by dual x-ray absorptiometry. The 65 patients with anorexia nervosa had significantly lower bone density (lumber spine 1.05 +or- 0.02 gm/sq cm, femoral neck 0.91 +or- 0.02 gm/sq cm), weight (43.3 +or- 0.9 kg), fat mass (7.01 +or- 0.57 kg), and fat-free (lean) mass (34.89 +or- 0.53 kg) than controls (all p 0.001), even after adjustments for differences in age (24.4 +or- 1.0 years, and height, 162.5 +or- 0.8 cm). In the 12 patients with primary amenorrhea, the reduction in bone density at the lumbar spine and femoral neck was greater than the reduction at the corresponding sites in the 37 patients with secondary amenorrhea (p = 0.001 and p = 0.04, respectively). A total of 16 patients took oral contraceptives for 61 +or- 9% of the duration of their illness whose mean bone density at the lumbar spine was greater than in the 49 patients without contraceptive exposure (p 0.01) but less than in controls (p 0.01). The 19 patients who exercised vigorously had higher bone density at the proximal femoral sites than sedentary patients. Patients with anorexia nervosa commencing around puberty may be at greater risk for fractures because they have lower bone density. A protective effect of oral contraceptives was found at the spine; a protective effect of weight-bearing exercise was found at the proximal femur. Thus, estrogen replacement therapy may be an important therapeutic option in this illness.