Relation between body composition and biochemical markers of bone turnoveramong early postmenopausal women

We studied the associations between body composition and biochemical marker s of bone formation and resorption among 1600 postmenopausal women, ages 45 -59. Multiple regression analyses were performed to examine the independent associations of fat mass, muscle strength (quadriceps strength), height, a nd whole-body bone mineral content (BMC) with biochemical markers of bone f ormation (serum osteocalcin) and resorption (urinary type I collagen crossl inked N-telopeptide [NTX]). Per interquartile range (IQR) (the difference b etween the 75th and 25th percentiles) increase in fat mass and whole-body B MC, the mean levels of osteocalcin decreased by 3 and 13%. respectively; NT X decreased by 5 and 21%, respectively. Fat mass and whole-body BMC were al so significantly associated with decreases in average osteocalcin and NTX Z -scores. By contrast, the mean levels of serum osteocalcin increased by 2 a nd 11%, respectively, per IQR increase in muscle strength and height; NTX i ncreased by 4 (not significant) and 14%, respectively. Both muscle strength and height were significantly associated with increases in average Z-score s. These exploratory analyses suggest that fat mass and whole-body BMC were associated with decreased bone turnover, whereas muscle strength and heigh t were associated with increased bone turnover.