Bone and vitamin D status in patients with anorexia nervosa

INTRODUCTION: The aim of the present study was to investigate bone status and biological mechanisms involved in the negative impact of anorexia nervosa (AN) on osteogenesis.

METHODS: A total of 30 AN patients from Aalborg University Hospital who underwent bone scans were included in a cross-sectional study. Biochemical data, bone scans (dual-energy X-ray absorptiometry (DXA)) as well as general health and medical information had been collected during the 2009-2011 period and stored via local and national clinical databases in Denmark, and from these databases we identified all patients with an AN diagnosis who underwent bone scans.

RESULTS: AN patients had a mean Z-score of -1.5 to -1.6 in lumbar spine and total hip, respectively. The hip Z-score decreased with duration of disease, and a positive correlation was seen between serum 25-hydroxy-vitamin D level and spine Z-score but not hip Z-score. Bone mineral density did not seem to change with time since diagnosis. Additionally, a negative correlation between serum 25-hydroxy-vitamin D levels and serum total alkaline phosphatase levels was found. A serum 25-hydroxy-vitamin D level below 50 nmol/l was associated with increased alkaline phosphatase levels.

CONCLUSION: Rather than clinical measures including BMI and biochemical measures disease duration was the main predictor of bone status. This implies that long-term disease should be a main factor in selecting patients for referral to DXA. Moreover, results from this study indicate normal osteoblastic response to malnutrition.

FUNDING: not relevant.

TRIAL REGISTRATION: The present study was not registered due to its register-based design. However, the study was approved by the Danish Data Protection Agency.