Pattern of bone mineral density in idiopathic male osteoporosis.

The mechanisms of male idiopathic osteoporosis are little known. We evaluated bone mineral loss by dual-energy X-ray absorptiometry and determined its cortical or trabecular nature in a cohort of men with idiopathic osteoporosis with fractures. Thirty-nine men (mean age 60 ± 13 years), with negative investigations for the cause of osteoporosis, were studied. All had fragility fractures: vertebral 51%, peripheral 25%, and both types 24%. Bone density was measured at the lumbar spine (L2-L4), total hip and whole body. The limb/axial skeleton (spine + hips) and hip/L2-L4 BMD ratios were calculated. Serum 25-hydroxy-vitamin D, PTH, bone alkaline phosphatase and CTX were measured. Bone mineral loss predominated at the lumbar spine (mean L2-L4 T-score -3 ± 0.93, mean total hip T-score -1.87 ± 0.75). Limb/axial skeleton and total hip/L2-L4 BMD were strongly correlated, but not hip and spine BMD. The ratio values were widely scattered, indicating markedly heterogeneous bone loss. Vitamin D, PTH, bone alkaline phosphatase and CTX levels did not differ between predominantly trabecular and cortical osteoporosis. Bone mineral density measurement in male idiopathic osteoporosis with fractures demonstrated that bone loss predominated in the spine and that it was very heterogeneous, principally affecting cortical or trabecular bone depending on the patient.