Osteoporosis and anorexia nervosa: relative role of endocrine alterations and malnutrition.

BACKGROUND AND AIM: Anorexia nervosa (AN) is a psychiatric disorder characterised by self-induced starvation or a very reduced caloric intake, and frequently by severe life-threatening protein calory malnutrition. Its physiological consequences include amenorrhea, estrogen deficiency and osteoporosis. Osteoporosis may develop as a consequence of a lack of estrogens, low calcium or vitamin D intake, hypercortisolemia or the duration of the illness. The aim of this study was to identify the best endocrinological and nutritional indicators of bone density.

SUBJECTS AND

METHODS

The study involved 49 young females with AN and malnutrition and 24 age-matched normal controls in whom AN had been excluded on the basis of a clinical evaluation using DSM IV criteria. We studied bone density in early osteopenia, a condition in which the potential risk of fractures is certainly high and traditionally related to a variety of endocrinological and nutritional factors.

RESULTS

Bone density was significantly lower in the AN than the control group in all of the examined bone districts: bone mineral density (BMD) spine 0.89 +/- 0.19 vs 1.27 +/- 0.2 (p<0.0001), BMD neck 0.75 +/- 0.14 vs 1.08 +/- 0.17 (p<0.001), BMD Ward 0.74 +/- 0.17 vs 1.12 +/- 0.11 (p<0.0001). Non-significant differences were found in the patients who had undergone previous estrogen medication. Body mass index (BMI) correlated with bone density, but caloric and calcium intake were not significant predictors. IGF-1, a known nutritionally dependent trophic bone factor, was significantly reduced in our patients but did not correlate with BMD. Like other authors, we found a close correlation between lean body mass and BMD in neck and spine. Physical exercise, urinary free cortisol osteocalcin and type I collagen-telopeptide (NTX) did not significantly correlate with the degree of osteopenia.

CONCLUSIONS

Our data suggest the importance of nutritional factors (particularly lean body mass and BMI) in determining bone mass, and the relatively limited importance of endocrinological factors with the exception of the duration of amenorrhea as an indirect indicator of endocrinological status.