Effects of Hormonal Status on Bone Density in Adolescent Girls*

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Abstract
Few data are available on bone density in late adolescence. We studied factors affecting peak bone density in females. Forty-three white girls, aged 13–20 yr, were studied. Integrated estrogen exposure over the pubertal years was obtained by a score based on physiological events known to reflect circulation estrogen levels. The subjects were selected to provide great variation in estrogen exposure. Bone mineral density (BMD) was measured by single photon absorptiometry (midradius) and dual photon absorptiometry (spine and first metatarsal of the foot). Weight, estrogen score, and testosterone levels were highly correlated with BMD of the spine, wrist, and foot (P < 0.05). Age correlated positively only with the BMD of the wrist. Twenty-four girls reaching ages 18–20 yr in the 2 yr of observation were divided into groups reflecting low (P < 0.05). This group weighed less and had lower weight to height ratio (P < 0.05), the lowest weight (P < 0.05) during adolescence, the highest age of menarche, and the highest amount of fiber in the diet (P < 0.05). These subjects were separated into low and high BMD groups. Those subjects with the lowest values for spine, wrist, and foot were found to have significantly lower estrogen exposure scores and lower weight/height ratios; in addition, low BMD of the foot was associated with higher activity levels. Thus, wrist and spine BMD are affected by estrogen exposure during adolescence and weight; foot BMD, in addition, was negatively affected by activity, suggesting that bone mass in the active adolescent is affected by the absence of estrogen exposure.