Practice sessionHEALTHCARE & MEDICAL EXAMSMEDICAL LICENSING

USMLE (United States Medical Licensing Examination) Practice Exam 02

Practice exam for USMLE (United States Medical Licensing Examination).

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Question 1 of 1000%

Time remaining120:00

Attempts allowedUnlimited

Difficulty mixE • M • H

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Question 1

MEDIUM

120:00

A 26-year-old woman is evaluated for recurrent calcium oxalate kidney stones. She reports intermittent flank pain for 2 years and drinks 1–2 glasses of water daily. She has no history of gout. Vital signs are normal. Laboratory studies show: serum calcium 9.4 mg/dL, serum bicarbonate 24 mEq/L, serum uric acid 4.8 mg/dL. A 24-hour urine collection shows hypercalciuria with normal serum calcium. Which of the following is the most likely mechanism contributing to her hypercalciuria?

Idiopathic hypercalciuria often reflects decreased proximal tubular calcium reabsorption that parallels sodium handling; reduced proximal Na+ reabsorption increases urinary Ca2+ excretion. Elevated PTH would typically raise serum calcium. Decreased 1α-hydroxylase would reduce calcium absorption and tends to lower urine calcium.

Select one answer

Decreased proximal tubular sodium reabsorption leading to decreased calcium reabsorption

Decreased renal 1α-hydroxylase activity leading to decreased intestinal calcium absorption

Increased aldosterone secretion leading to increased potassium excretion and calcium retention

Increased parathyroid hormone secretion causing increased bone resorption

Increased proximal tubular citrate reabsorption leading to hypocitraturia

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USMLE (United States Medical Licensing Examination) Practice Exam 02

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