Monday, June 24, 2013

Bone Metabolism in Adolescent Boys with Anorexia Nervosa

For over 25 years, Dr. David Herzog, Emeritus Professor of Psychiatry at Harvard Medical School, has worked closely with the Neuroendocrine Unit at Massachusetts General Hospital (MGH) to better understand the biology of eating disorders. Research conducted by this team found that bone loss is a serious complication for the majority of adolescent girls and adult women with anorexia nervosa, placing them at increased risk of fracture and permanent disability. 

Dr. Herzog and his team in the Neuroendocrine Unit went on to conduct the first controlled study of bone mineral density in boys with anorexia. Thirty-four boys between the ages of 12 and 19 participated; seventeen of the boys had anorexia nervosa and 17 were healthy controls.  Dual energy x-ray absorptiometry (DXA) was used to measure participants’ bone density. Blood was drawn for IGF-1 (insulin-like growth factor 1); testosterone; SHBG (sex hormone-binding globulin); estradiol (a main form of estrogen); the appetite-regulating hormones ghrelin, PYY, and leptin; and biochemical markers of bone formation and bone resorption. The participants completed questionnaires that assessed their food intake and levels of physical activity.

The boys with anorexia nervosa had lower bone mineral density at the spine, hip, femoral neck, trochanter, intertrochanteric region, and whole body, compared with controls. The hip and its subregions were affected by low bone density at least as severely as the spine. The markers of bone formation and bone resorption were reduced in the boys with anorexia compared with controls, who were in a state of increased bone turnover. Low body mass index and lean mass and low testosterone levels were important predictors of low bone mineral density.

The findings of this study are concerning for low bone mineral density and possibly a decreased rate of bone mass accrual during adolescence, a period characterized by marked increases in  bone accrual toward achievement of peak bone mass. This raises questions regarding bone health and fracture risk in later life. Because body mass index is a key predictor of low bone density, emphasizing weight recovery is critical.

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