استئوپنی در بی اشتهایی عصبی: مکانیسم های خاص از دست رفتن استخوان

Osteopenia is a well recognized medical complication of anorexia nervosa (AN). The mechanism of bone loss is not fully understood and there is uncertainty about its management. New markers of bone turnover have been developed. C-terminal type 1 propeptide (PICP) is a measure of bone formation and urinary pyridinolines such as deoxypyridinoline (DPYRX) and serum carboxyterminal crosslinked telopeptide (ICTP) are markers of bone resorption. The aim of this study was to examine these bone markers in patients with AN. Twenty female patients with AN and 12 healthy controls were included in the study. Bone mineral density (BMD) of AN patients was measured by dual energy X-ray absorptiometry (DEXA). Lumbar bone density was significantly reduced in the AN group compared to standardised values of thirty year old adults (t-score 83.2%, S.D. 12.1). Femoral neck bone density showed an even greater reduction (t-score 79.4%, S.D. 13.5). We found a significant negative correlation between femoral BMD and the duration of the illness. Femoral BMD correlated significantly with minimal body weight (r(16)=0.504, p=0.033). The markers of bone resorption were significantly higher in the patients with AN compared to the values of the control group (ICTP t(30)=−2.15, p=0.04, DPYRX t(25)=−2.26, p=0.033), whereas the markers of bone formation did not differ significantly between the groups. AN appears to be a low turn over state associated with increased bone resorption without concomitant bone formation. This pattern differs from osteopenia in menopausal women and should, therefore, lead to the development of specific therapeutic strategies in AN associated osteopenia. Hormone replacement therapy as well as calcium and vitamine D-supplementation are so far discussed controversially. Long-term treatment studies are warranted.

Anorexia nervosa (AN) is a common chronic disorder with an estimated prevalence of 1% in female adolescents and young women (APA, 1993). The restrictive eating pattern is associated with profound metabolic complications, including prolonged amenorrhea. Long-term studies up to 10 years demonstrate that only 42–48% of patients recover to normal weight and attain regular menstrual function (Herzog et al., 1997). Regarding the chronicity and severity of AN, it is crucial to study its putative long-term metabolic consequences. A serious complication of AN is osteopenia, defined by a bone density of more than 2 standard deviations below the normal mean. Bone loss is often rapid Rigotti et al., 1984, Biller et al., 1989 and Bachrach et al., 1991 and affects adolescents, in whom there is a significant reduction in peak bone mass achieved during the critical years of bone formation Ayers et al., 1984 and Bachrach et al., 1990. Wether such deficiency is permanent or can be restored remains unanswered. As a consequence, young anorexic women are at risk of early osteoporosis, kyphosis, and spontaneous fractures at multiple sites Brotman and Stern, 1985, Szmukler et al., 1985 and Rigotti et al., 1991. So far the exact mechanisms are not fully clarified. Several factors such as malnutrition, reduced body weight, amenorrhea, and hypercortisolaemia seem to be involved. There are only few data available concerning bone turnover and mechanisms of osteopenia in this population. New markers of bone turnover have been developed. C-terminal type 1 propeptide (PICP) is a measure of bone formation and urinary pyridinolines such as deoxypyridinoline (DPYRX) and serum carboxyterminal crosslinked telopeptide (ICTP) are markers of bone resorption. The aim of this study was to investigate the specific mechanisms of anorexia associated bone loss by examining these bone markers in patients with AN.