26th April 2024

A 60-year-old woman presents with a year-long history of generalised bone pain, fatigue, and frequent episodes of confusion.

A 60-year-old woman presents with a year-long history of generalised bone pain, fatigue, and frequent episodes of confusion. Recently, she has had several episodes of kidney stones. Her past medical history includes osteoporosis and peptic ulcer disease. On examination, she is alert but appears fatigued. There is tenderness on palpation over her lumbar spine and pelvis.

Investigations:

Serum calcium: 3.1 mmol/L (2.2–2.6)

Serum phosphate: 0.7 mmol/L (0.8–1.5)

Serum alkaline phosphatase: 300 IU/L (25–115)

Parathyroid hormone (PTH): Elevated

24-hour urinary calcium: Elevated

Which is the most likely cause of her presentation?