Lateral radiographs were examined for thoracic and lumbar morphometric vertebral fractures as well as nonvertebral fractures by a musculoskeletal radiologist who was blinded to the DXA results. Vertebral fractures were identified using semiquantitative morphometry.18 A fracture was defined as a decrease of at least 25% in any vertical height measurement (ie, anterior, mid, and posterior) when compared to adjacent vertebrae. Body mass index (BMI) and FEV1, expressed as a percentage of normal predicted values, were measured at the time of DXA testing. Blood was drawn on the day of the DXA scan for biochemistry measurements, which included ionized calcium, phosphate, magnesium, 25-OH vitamin D (radioimmunoassay; DiaSorin; Stillwater, MN), 1,25-dihyroxyvitamin D (calf-thymus receptor assay; Varian; Palo Alto, CA), growth hormone (Ultrasensitive human growth hormone Access assay; Beckman Coulter; Brea, CA), bioavailable testosterone (radioimmunoassay), thyroid-stimulating hormone (Access HYPERsensitive human thyroid-stimulating hormone assay; Beckman Coulter), parathyroid-stimulating hormone (intact parathyroid hormone SP immunoradiometric assay; DiaSorin), osteocalcin (Osteocalcin radioimmunoassay; DiaSorin), insulin-like growth factor-1 (IGF-1 immunoradiometric assay; Nichols Institute Diagnostics; San Clemente, CA), creatinine, and estrogen (Access Estradiol assay; Beckman Coulter). Glucocorticoid exposure was determined from clinic charts. Other variables such as pancreatic status, the presence of CF-related diabetes, sputum bacteriology, and pulmonary function measurements were obtained from the Toronto CF Database.