Effects of Anorexia Nervosa on Peak Bone Mass

Study Summary

Teenage girls with anorexia nervosa (AN) are at risk for low bone density and low rates of bone accrual, raising concerns regarding acquisition of peak bone mass, an important determinant of future bone health and fracture risk. Important factors contributing to low bone density in AN include low levels of estrogen and insulin like growth factor-1 (IGF-1). While estrogen is important for preventing bone loss, IGF-1 is important for optimizing bone formation. We have shown in a previous study that replacement of estrogen is effective in increasing bone density in teenage girls with AN; however, this increase in bone density remains lower than that seen in normal-weight controls over the same duration, and residual deficits persist. Importantly, the impact of administering replacement doses of IGF-1 with estrogen replacement has not been studied in teenagers with AN. This study will examine the impact of administering recombinant human (rh) insulin like growth factor-1 (rhIGF-1) with estrogen (to mimic pubertal levels of these hormones) versus administration of estrogen alone on bone metabolism in adolescent girls with anorexia nervosa (AN). One aim of this proposal is to investigate whether co-administration of insulin like growth factor-1 (rhIGF-1) with physiologic estradiol replacement to adolescent girls with AN will increase BMD (bone mineral density) more than estrogen monotherapy, and whether bone mass will approach that seen in healthy adolescent girls. An additional aim is to determine whether co-administration of rhIGF-1 with estradiol to mimic the normal pubertal milieu stimulates bone formation through an IGF-1 mediated anabolic effect, increases bone density to a greater extent than estrogen monotherapy, and improves bone mass accrual to approach that in healthy controls. The impact of rhIGF-1 +estradiol versus estradiol alone on bone microarchitecture will also be assessed.

Primary Outcome

Change in lumbar spine BMD z-score over 12 months as assessed by dual energy x-ray absorptiometry (DXA) The z-score indicates the number of standard deviations that BMD is away from the mean for age, sex and race. A z-score of 0 is equal to the mean with negative numbers indicating values lower than the mean and positive values higher values. A positive change in z-scores indicates a favorable outcome whereas a negative change in z-scores indicates an unfavorable outcome.

Interventions

• DRUG RhIGF-1 with transdermal 17-beta estradiol
• DRUG Placebo and transdermal 17-beta estradiol