Treatment of anorexia nervosa is associated with increases in bone mineral density, and recovery is a biphasic process involving both nutrition and return of menses.

BACKGROUND

Recovery from osteoporosis in anorexia nervosa (AN) is uncertain.

OBJECTIVE

The purpose of this study was to understand the changes in bone mineral density (BMD) in women with AN and the mechanisms of recovery from osteopenia.

DESIGN

We studied BMD and markers of bone formation and resorption, osteocalcin and N-telopeptide (NTX), in patients with AN (n=28) who were following a behavioral weight-gain protocol.

RESULTS

Anorexic patients experienced significant percentage increases in BMD (4.38 +/- 7.48% for spine; 3.77 +/- 8.8% for hip; P<0.05 for both) from admission until recovery of 90% ideal body weight, achieved over 2.2 mo. NTX concentrations were higher in patients with AN at admission than in healthy control subjects (n=11; 69.0 +/- 31.09 and 48.3 +/- 14.38 nmol/mmol creatinine, respectively; P<0.05) and in reference control subjects (n=30; 69.0 +/- 31.09 and 37.0+/-6.00 nmol/mmol creatinine, respectively; P<0.001). In weight-recovered subjects with AN, osteocalcin increased (from 8.0 +/- 3.05 to 11.2 +/- 6.54 ng/mL; P<0.05), whereas NTX remained elevated (from 69.0 +/- 31.09 to 66.7 +/- 45.5 nmol/mmol creatinine; NS). A decrease in NTX (from 70.7 +/- 40.84 to 45.9 +/- 22.72 nmol/mmol creatinine; NS) occurred only in the subgroup of subjects who regained menses with weight recovery.

CONCLUSIONS

Nutritional rehabilitation induces a powerful anabolic effect on bone. However, a fall of NTX and a shift from the dominant resorptive state, which we postulate involves full recovery, may involve a hormonal mechanism and require a return of menses. Nutritional rehabilitation appears to be critical to bone recovery and may explain the ineffectiveness of estrogen treatment alone on BMD in the cachectic state.