Clinical meaning
Osteoporosis reflects a fundamental disruption in the RANK/RANKL/OPG signaling axis that governs bone remodeling. RANKL, expressed by osteoblasts, binds RANK on osteoclast precursors to stimulate differentiation and activation. Osteoprotegerin (OPG), a decoy receptor, competitively inhibits this interaction. Estrogen upregulates OPG and suppresses RANKL; its loss during menopause shifts the balance toward excessive osteoclastogenesis. Glucocorticoids compound this by directly inhibiting osteoblast function, inducing osteocyte apoptosis, and decreasing intestinal calcium absorption. The clinician must prescribe evidence-based pharmacotherapy (antiresorptive or anabolic agents), interpret bone density and fracture risk data, manage drug holidays and transitions, and address secondary causes through comprehensive workup.
Diagnosis & workup
Diagnostics & workup: - Order DEXA scan of lumbar spine and proximal femur; interpret T-scores for diagnosis and Z-scores for premenopausal/male patients - Calculate FRAX score to guide treatment decisions (treat if 10-year hip fracture risk ≥3% or major osteoporotic fracture risk ≥20%) - Order comprehensive metabolic workup: 25-hydroxyvitamin D, serum calcium, phosphorus, intact PTH, TSH - Order 24-hour urine calcium to assess absorption and excretion - Consider bone turnover markers (CTX for resorption, P1NP for formation) to monitor treatment response - Order vertebral fracture assessment (VFA) with DEXA or lateral thoracolumbar X-ray in patients with height loss ≥1.5 inches - Rule out secondary causes: SPEP/UPEP (myeloma), celiac panel, cortisol testing as indicated - Screen for fall risk using Timed Up and Go (TUG) test