BMI and Length of Disease Predict Bone Turnover in AN

Long-term anorexia nervosa (AN) and a low body mass index (BMI) lead to a breakdown of the essential balance of bone formation and resorption (European J Clin Nutr 2003; 57:1262), according to the results of a recent case-controlled study. University of Bonn scientists discovered this pattern after evaluating 51 women with AN and 51 control subjects matched for age, sex, and height.

AN patients had lower BMIs, lower fat mass, lower fat-free mass, and lower muscle mass than women in the control group. In addition, serum levels of osteocalcin (a marker of bone formation) were lower, and serum levels of C-telopeptide (CTx, a marker of bone resorption) were higher in patients than in controls. Finally, a ratio of these two markers, which provides an index reflecting the balance of bone formation and remodeling, was elevated among patients but not controls. The AN patients had enhanced serum calcium and cortisol levels, and reduced serum levels of several hormones, including thyroid hormones, insulin, and leptin.

BMI and duration of disease were independent predictors of the CTx/osteocalcin ratio in the patients with AN. Use of oral contraceptives had no effect upon the ratio in patients or controls.