Bone Mineral Density (BMD)
A measurement of the mineral content in bone, used to diagnose osteoporosis and assess fracture risk. BMD is measured by DEXA scan and expressed as T-scores and Z-scores. Monitoring BMD changes is essential for evaluating the effectiveness of bone-active peptide therapies.
Technical Context
BMD is measured in g/cm² and compared to reference populations: T-score (comparison to young adult peak bone mass — used for postmenopausal women and men ≥50) and Z-score (comparison to age/sex-matched population — used for premenopausal women, men <50, and children). DEXA measurement sites: lumbar spine L1-L4 (cancellous bone predominant — responsive to treatment changes), femoral neck (predictive of hip fracture), total hip (integrated cortical/cancellous), and distal radius (when spine/hip sites are invalid). For PTH analogue therapy (teriparatide, abaloparatide): spine BMD increases approximately 8-13% over 18-24 months, with smaller hip BMD increases. Monitoring interval: typically 1-2 years during treatment. Minimum significant change (MSC) at each DEXA site determines whether a real BMD change has occurred vs measurement variability — typically approximately 3-5% at the spine and 4-6% at the hip.