Metabolic Bone Diseases and Calcium Homeostasis — WACS Viva & Clinical Scenarios (Endocrinology, Diabetes, and Metabolism)

Exam-style metabolic bone diseases and calcium homeostasis viva scenarios with examiner probes and model answers for Internal Medicine candidates.

Scenarios covered

• SCENARIO 1: A 58-year-old male with known squamous cell carcinoma of the lung is brought to the emergency department with severe lethargy, confusion, constipation, and polyuria. Laboratory evaluation reveals a corrected total serum calcium of 3.72 mmol/L, serum phosphate of 0.70 mmol/L, suppressed intact parathyroid hormone (<0.6 pmol/L), and serum creatinine of 210 micromol/L. Outline the immediate resuscitation protocol, sequential pharmacological interventions, and monitoring parameters for this acute hypercalcaemic crisis.
• SCENARIO 2: A 64-year-old postmenopausal female undergoes Dual-energy X-ray Absorptiometry (DXA) screening following a low-trauma distal radius fracture. The DXA scan demonstrates a lumbar spine (L1-L4) T-score of -2.9, femoral neck T-score of -2.6, and total hip T-score of -2.4. Detail the diagnostic interpretation, comprehensive laboratory workup for secondary causes of osteoporosis, and the individualized management plan including pharmacotherapy selection, administration counseling, and monitoring.
• SCENARIO 3: A 42-year-old female presents with severe perioral paresthesia, muscle cramping, and painful carpopedal spasm four days after undergoing a total thyroidectomy for multinodular goitre. Her corrected serum calcium is 1.68 mmol/L, serum phosphate is 1.95 mmol/L, and serum intact PTH is 0.8 pmol/L (reference range 1.6 to 6.9 pmol/L). Describe the clinical elicitation of latent tetany signs, the immediate intravenous calcium stabilization protocol, and long-term outpatient replacement therapy.
• SCENARIO 4: Contrast the pathophysiology, biochemical profiles, and radiographic hallmarks of Osteomalacia with Paget Disease of Bone (Osteitis Deformans). Specify the expected levels of serum calcium, phosphate, total and bone-specific alkaline phosphatase, intact parathyroid hormone, and 25-hydroxyvitamin D, alongside characteristic skeletal radiograph findings and initial medical management for each condition.
• SCENARIO 5: A 52-year-old male with end-stage renal disease on maintenance haemodialysis for six years presents with diffuse bone pain, proximal muscle weakness, severe pruritus, and multiple vascular calcifications on abdominal radiographs. Laboratory investigations show corrected serum calcium 2.10 mmol/L, serum phosphate 2.35 mmol/L, intact PTH 880 pg/mL, and markedly elevated bone-specific alkaline phosphatase. Detail the pathophysiological evolution from secondary to tertiary hyperparathyroidism in Chronic Kidney Disease - Mineral and Bone Disorder (CKD-MBD), diagnostic differentiation of renal osteo