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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