Hyperparathyroidism

A 55-year-old man with CKD Stage 4 (eGFR 22 mL/min/1.73m²) due to IgA nephropathy is referred for pre-emptive kidney transplant evaluation. His serum calcium is 8.2 mg/dL, phosphate 5.8 mg/dL, and parathyroid hormone (PTH) is 380 pg/mL. Which of the following best describes the pathophysiology of secondary hyperparathyroidism in this patient?

A 58-year-old woman from Mumbai presents with a 6-month history of polyuria, polydipsia, and recurrent nephrolithiasis. She reports fatigue and cognitive difficulties. On examination, she appears anxious. Laboratory investigations reveal: serum calcium 11.8 mg/dL (normal 8.5–10.5), phosphate 2.8 mg/dL (normal 2.5–4.5), alkaline phosphatase 92 U/L (normal 30–120), PTH 185 pg/mL (normal 15–65), 24-hour urinary calcium 420 mg/day (normal <300). Serum creatinine is 1.1 mg/dL. Abdominal ultrasound shows a 1.2 cm echogenic lesion in the inferior pole of the left thyroid lobe. What is the most appropriate next step in management?

A 52-year-old man from Delhi presents with a 3-month history of bone pain, muscle weakness, and recurrent pathological fractures of the ribs and vertebrae. He reports nausea and constipation. On examination, he has generalized muscle weakness and tenderness over the spine. Laboratory findings: serum calcium 12.4 mg/dL (normal 8.5–10.5), phosphate 2.1 mg/dL (normal 2.5–4.5), alkaline phosphatase 156 U/L (normal 30–120), PTH 320 pg/mL (normal 15–65), 25-hydroxyvitamin D 18 ng/mL (normal >30), magnesium 1.6 mg/dL (normal 1.7–2.2). Serum creatinine 1.3 mg/dL. X-ray shows generalized osteopenia with subperiosteal resorption of the phalanges. What is the primary pathophysiological mechanism underlying the skeletal manifestations in this patient?

A 58-year-old woman from rural Maharashtra presents with a 6-month history of polyuria, polydipsia, and recurrent kidney stones. On examination, she is alert but appears dehydrated. Laboratory investigations reveal: serum calcium 11.8 mg/dL (normal 8.5–10.5), phosphate 2.8 mg/dL (normal 2.5–4.5), alkaline phosphatase 95 U/L (normal 30–120), serum creatinine 1.4 mg/dL, and 24-hour urinary calcium 380 mg/day (normal <250). Intact PTH level is 185 pg/mL (normal 10–65). Ultrasound abdomen shows bilateral renal calculi. What is the most likely diagnosis?

A 55-year-old woman presents with a 6-month history of bone pain, muscle weakness, polyuria, and recurrent nephrolithiasis. Laboratory studies reveal serum calcium 12.8 mg/dL, phosphate 2.1 mg/dL, and elevated intact PTH at 285 pg/mL. Lateral skull radiograph demonstrates the classic appearance marked as **A** in the diagram—a diffuse mottled appearance with blurring of the inner and outer tables and granular diploic space with alternating foci of lucency and sclerosis. Which of the following best describes the pathophysiologic basis for this radiographic finding in primary hyperparathyroidism?