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Introduction: In Germany more than 6 million persons are affected by osteoporosis which is characterized by low bone density and microarchitectural deterioration of bone tissue leading to increased bone fragility. Mostly, postmenopausal women suffer from osteoporosis but it can also occur in men, children and adolescents - as a sequela of underlying diseases like anorexia nervosa (AN). AN is an eating disorder characterized by self-induced weight loss and underweight concerning an increasing number of female adolescents. One of the consequences is osteoporosis occuring in more than 50 per cent of anorectics. Voluntary starvation leads to decreased peak bone mass via low calcium intake, vitamin D deficiency and low body weight. Elevated cortison levels, decreased IGF-1 and excessive physical exercise contribute to osteoporosis as well as disturbed hypothalamic-hypophysary-ovarian axis.
Material and methods: Our cross-section study on the effects of AN on quantitative ultrasound (QUS) included 46 female anorectic patients aged between 11 and 25 years and 124 healthy controls of the same age. In all participants we collected anamnestic data by means of a standardized questionnaire, as well as the QUS parameters speed of sound (SOS), broadband ultrasound attenuation (BUA) and stiffness index (SI) using the Achilles Plus ultrasonometer (GE/ Lunar) on the os calcis. Girls with other bone affecting diseases were excluded. We used matched-pair analysis to compare the ascertained data. Linear multiple regression analysis was performed to investigate combined influences of the different variables on QUS parameters.
Results: After matched-pair analysis anorectics had significant lower BUA parameters than controls. There were no significant differences between the two study groups for SOS and SI. We found a significant negative correlation between QUS parameters and duration of AN and between age of menarche and SOS. Duration of amenorrhea showed a trend towards lower QUS parameters (not significant). Body height and frequency of physical exercise were positively correlated with QUS parameters. Use of contraceptive pills showed higher QUS results in all participants but a strong trend towards worse QUS results in anorectics. There was no significant correlation between deepest body mass index (BMI) and intensity of smoking in comparison to QUS parameters.
Discussion: Our study is the first matched-pair analysis using multiple matching parameters to examine loss of bone mass in AN by means of QUS. Like in other studies BUA is the only QUS parameter to be significantly lower in anorectis compared to healthy controls. Using QUS a deterioration in bone quality in the course of AN can be demonstrated.