MS-2839

MS-2839

A 68-year-old woman is referred to haematology via the 2-week wait pathway due to worsening thoracic back pain that started 3 weeks ago. There is no history of trauma. Upon examination, the pain is exacerbated by movement and occurs even at rest and during bedtime. Her blood test results show a Hb level of 97 g/L (female normal range: 115-160 g/L), platelets of 200 * 109/L (normal range: 150-400 * 109/L), and WBC count of 4.0 * 109/L (normal range: 4.0-11.0 * 109/L). Additionally, her calcium level is 2.9 mmol/L (normal range: 2.1-2.6 mmol/L), phosphate level is 1.2 mmol/L (normal range: 0.8-1.4 mmol/L), magnesium level is 0.8 mmol/L (normal range: 0.7-1.0 mmol/L), TSH level is 5.0 mU/L (normal range: 0.5-5.5 mU/L), and free thyroxine (T4) level is 16 pmol/L (normal range: 9.0-18 pmol/L). Based on the likely diagnosis, what is the underlying pathophysiology that causes hypercalcemia?