Serum osteocalcin levels in postmenopausal obese women

In epidemiology of osteoporosis, obesity is to be considered one of its protecting factors. However there are in the literature discordant opinions: some authors describe a protective effect of obesity on the trabecular bone, others on the cortical one, others no effects at all and others finally a positive influence on both the trabecular and the cortical bone. However, only few studies on obesity's impact on bone metabolism are available. Bone mineral density at forearm and serum osteocalcin levels, a specific and sensitive marker of bone turn-over, in a group of postmenopausal obese women with those of a nonobese control group were compared. Obese women showed higher densitometric measurements than nonobese, but only the values of the third distal site of forearm resulted higher in a significant way. Serum osteocalcin values were similar between the two groups but the obese women showed a greater dispersion of the values (8.15 +/- 4.96 ng/ml) compared to nonobese (8.35 +/- 1.63 ng/ml). This high variability suggests an heterogeneity of bone turn-over in obese subjects and could explain the discordant results of the literature.