Correlates and determinants of bone mineral content and density in healthy adolescent girls

The relationships between whole-body and lumbar spine bone mineral content and density, and measures of chronologic age, body composition, physical activity, cardiorespiratory and strength fitness, gynecologic attributes, sexual maturity, and endocrine status were studied in 35 healthy menarcheal girls (14-18 years of age). Body mass (0.464 < r < 0.704), growth hormone (-0.34 < r < -0.42), and one-repetition maximum double-leg press strength (0.343 < r < 0.467) were significantly (p < 0.05) correlated with each of the five bone mineral measures. Multiple regression analysis indicated that body mass accounted for the largest significant proportion of the explained variance (30.2-68.2%) in each of the five bone mineral measures. Age at first menses accounted for a smaller but still significant proportion of the variance in whole-body bone mineral content (4.05%) and lumbar spine bone mineral content (8.06%). Growth hormone entered the regression model as an important predictor of whole-body bone mineral content, accounting for 3.51% of the explained variance in this variable. Age, cardiorespiratory fitness, level of habitual activity, and strength did not contribute significantly to the explained variance in any of the bone mineral measures. Body mass appears to be the single most important determinant of bone mineral among females during this developmental period.