Pathophysiology and diagnosis of osteoporosis in aging men

Osteoporotic fractures in older men are a major public health problem due to their morbidity, mortality and costs. Older men have a lower fracture risk than age-matched women for several reasons. Young men have larger bones than women even after adjustment for differences in body size. Age-related cortical thinning is lower in magnitude in men than in women because in men, endocortical expansion is more efficiently offset by periosteal apposition. The principal mechanism of trabecular bone loss in men is trabecular thinning in contrast to trabecular perforation and loss in women. The definition and the diagnostic criteria of osteoporosis in men are still subject to debate and controversy. In men aged 50 and older, osteoporosis may be diagnosed if the sex-specific T-score of the lumbar spine, total hip, or femoral neck is -2.5 or less. In certain circumstances, the one-third distal radius may also be utilized. Assessment of clinical risk factors can help clinicians identify asymptomatic men at risk for low bone mineral density (BMD). For instance, in men with prostate cancer, both surgical bilateral orchidectomy and androgen-deprivation therapy result in rapid bone loss and high risk of fracture. The fracture risk assessment tool (FRAX) helps identify individuals at high risk of fracture on the basis of several clinical criteria associated with an increased fracture risk regardless of BMD. Especially in the elderly, the assessment of the risk of fracture must include assessment of the risk of falls. IBMS BoneKEy. 2008 October;5(10):370-380. 2008 International Bone & Mineral Society Osteoporosis in Aging Men – Burden of the Disease Osteoporosis-related fractures (fragility fractures) in older men are a major public health problem. There are fewer fragility fractures in men than women because men have stronger bones and shorter life expectancy (1-2). The risk of fragility fracture in a man is equal to a risk of fracture in a woman who is five to ten years younger, except for old men who have a higher risk of death than that of fracture (3-5). Currently, an increase in life expectancy results in a higher number of men at high risk of fracture and a higher number of fractures in this population (1-2). Conversely, the agespecific incidence of fractures does not increase in more recent generations (3;5-7). Fragility fractures in older men are responsible for 20 to 30% of the overall costs of fractures in the elderly (8). The proportion of years of life lost after a fragility fracture is significantly higher in men than in women (9). By contrast, data on the significantly higher mortality after fracture in men in comparison with women should be interpreted more cautiously because of the difference in life expectancy. Pathophysiology of Bone Fragility in Men Bone size and strength in young adults Older men have a lower risk of fracture than age-matched women because: 1) young men have stronger bone than women and 2) age-related loss of bone strength is lower in magnitude in men than women. In comparison with young women, young men have larger bones (higher external diameter, higher cross-sectional area [CSA]) due to higher cortical area and higher medullary area (11-12). These differences persist after adjustment for body size. Consequently, men have higher peak areal bone mineral density (aBMD). However, the proportion of total bone area occupied by IBMS BoneKEy. 2008 October;5(10):370-380 http://www.bonekey-ibms.org/cgi/content/full/ibmske;5/10/370 doi: 10.1138/20080342