Chronic Kidney Disease USMLE Step 1 Practice Question
A 59-year-old man with stage 4 chronic kidney disease presents with diffuse bone pain and pruritus. Vital signs: BP 148/92 mmHg, HR 88/min, RR 16/min, temp 37°C. Laboratory studies reveal calcium 7.2 mg/dL, phosphate 5.8 mg/dL, PTH 287 pg/mL, and creatinine 3.1 mg/dL. Renal ultrasound shows normal-sized kidneys without obstruction. He denies recent fractures. Which mechanism best explains the elevated parathyroid hormone?
Answer choices
- APrimary autonomous secretion from a parathyroid adenoma
- BExcess intestinal calcium absorption due to increased calcitriol
- CSuppression of fibroblast growth factor 23
- DParaneoplastic PTH related peptide secretion by a renal tumor
- EPhosphate retention and reduced 1 alpha hydroxylase activity cause secondary hyperparathyroidismCorrect answer
- FIncreased renal sensitivity to PTH with enhanced proximal tubule calcium reabsorption
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