Chronic Kidney Disease USMLE Step 1 Practice Question
A 62-year-old man with stage 4 chronic kidney disease presents with diffuse bone pain and pruritus. Vital signs: BP 152/88, HR 82, RR 16, Temp 37°C, SpO2 98%. Laboratory studies reveal calcium 7.2 mg/dL, phosphate 5.8 mg/dL, PTH 612 pg/mL, and creatinine 3.4 mg/dL. Renal ultrasound shows normal kidney size without obstruction. He denies recent medication changes. Which mechanism best explains the elevated parathyroid hormone?
Answer choices
- APrimary autonomous parathyroid adenoma
- BExcess calcitriol production by the diseased kidney
- CDestruction of parathyroid glands by autoimmunity
- DEctopic PTH production by renal cell carcinoma
- ESecondary hyperparathyroidism due to phosphate retention and reduced calcitriolCorrect answer
- FTertiary hyperparathyroidism with autonomous PTH secretion from chronic secondary stimulation
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.