A 62-year-old postmenopausal woman from Delhi presents with acute onset severe back pain after a minor fall from standing height. On examination, she has kyphosis and loss of height (152 cm, previously 158 cm). X-ray shows a wedge-shaped compression fracture of T12 vertebra with 40% loss of vertebral height. DEXA scan reveals T-score of −2.8 at the lumbar spine. Laboratory investigations show: serum calcium 8.2 mg/dL, phosphate 3.5 mg/dL, alkaline phosphatase 68 U/L, 25-OH vitamin D 18 ng/mL. What is the most appropriate next step in management?