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Catherine M. Gordon, MD, MSc |
Despite being emaciated, patients with anorexia nervosa have strikingly high levels of fat within their bone marrow, report researchers at Children’s Hospital Boston (Journal of Bone and Mineral Research, February 2010). This seemingly paradoxical finding, based on MRI imaging of the knees, confirms previous observations in mice with clinical signs similar to anorexia nervosa.
The researchers, led by endocrinologist Catherine M. Gordon, MD, MSc, director of Children’s Bone Health Program, imaged 20 girls and young women with anorexia, averaging 16 years of age, and 20 healthy controls. Images were read by radiologists unaware of the patients’ clinical status. Compared with controls, patients with anorexia had markedly increased fat content (“yellow” marrow) and less than half as much healthy red marrow in both the femur and tibia.
Dr. Gordon believes that the hormonal alterations caused by malnutrition push mesenchymal stem cells in the marrow to form fat cells rather than bone-forming osteoblasts. This may explain why patients with anorexia have bone loss, which is a problem in growing adolescents who should be maximally forming bones.
Why does this occur? One speculation is that the body stores fat in the marrow in an attempt to preserve energy and warmth (hypothermia is a major reason for hospitalization in anorexia). Dr. Gordon now wants to see how closely fat in the bone marrow correlates with bone density, and whether measuring fat noninvasively through MRI scans could help assess the efficacy of hormonal therapies aimed at improving bone mass, now being tested in several studies at Children’s.
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