Biochemical markers of bone turnover in men.

Although osteoporosis in men has been recently recognized as a public health problem, the mechanisms leading to bone loss are still poorly understood. Longitudinal studies of bone mineral density suggest an acceleration of bone loss after 70 years of age. Histomorphometric data concerning age-related changes of bone turnover in men are limited, including few men over 70 years and have been restricted to the trabecular envelope of bone biopsies. Most measurements of biochemical markers of bone turnover have been performed in small cohorts of limited age range, and results obtained in large cohorts are scanty. Levels of markers of bone formation and of bone resorption are very high in men aged 20-30 years which corresponds to the late phase of formation of peak bone mass, and then declines, reaching their lowest levels between 50 and 60 years. Data on bone turnover markers in elderly men are discordant. Concentrations of bone formation markers remain stable, decrease slightly, or even increase marginally. Markers of bone resorption increase in some studies, mainly after 70 years of age, in line with acceleration of bone loss in this age range. This discordance between studies can result from different reasons. The increase of bone turnover may be limited to a subgroup of elderly men. In addition, urinary levels of bone resorption markers depend on the rate of bone turnover, on pre-renal and renal catabolism of peptides released from bone matrix, on glomerular filtration rate, as well as unit of expression of their results (per 24 hours per urinary creatinine mass, per glomerular filtrate volume). In elderly men, biochemical bone markers are negatively correlated with bone mineral density. Longitudinal studies are not yet available on the relationship among bone turnover markers, rate of bone loss, and fracture. In conclusion, in elderly men, age-related bone loss seems to result from increased bone resorption which is not matched by increased bone formation. Thus, antiresorptive therapy may be of interest in the prevention and treatment of osteoporosis in men. Further studies are necessary to determine if bone resorption markers predict the risk of fragility fractures in elderly men.