T-Score (Bone Density)
A comparison of an individual's bone mineral density to the average peak bone density of a healthy young adult. A T-score of -1.0 or above is normal, -1.0 to -2.5 indicates osteopenia, and -2.5 or below indicates osteoporosis. T-scores guide decisions about starting bone-active peptide therapies.
Technical Context
T-score = (patient's BMD − young adult mean BMD) / young adult SD. WHO classification: normal (T ≥ −1.0), osteopenia (−2.5 < T < −1.0), osteoporosis (T ≤ −2.5), and established/severe osteoporosis (T ≤ −2.5 with fragility fracture). For every 1.0 SD decrease in BMD, fracture risk approximately doubles. However, T-score alone has limited predictive power for individual fracture risk — most fractures occur in patients with osteopenia rather than osteoporosis (because many more people have osteopenia). FRAX integration: combining T-score with clinical risk factors provides better fracture prediction than T-score alone. Treatment thresholds vary by country: US (NOF/AACE) — treat if T ≤ −2.5 OR fragility fracture OR FRAX ≥3% hip/≥20% major osteoporotic; UK (NOGG/NICE) — FRAX-based, age-dependent thresholds. PTH analogue therapy is generally reserved for patients with T-scores well below −2.5, multiple fractures, or failed anti-resorptive therapy.