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Practice sessionHEALTHCARE & MEDICAL EXAMSMEDICAL LICENSING

USMLE (United States Medical Licensing Examination) Practice Exam 01

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

Active sessionUSMLE practice testUSMLE practice examUSMLE practice questionsUnited States Medical Licensing Examinationmedical licensing exam+6
Question 1 of 1000%
Time remaining120:00
Attempts allowedUnlimited
Difficulty mixE • M • H
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Question 1

MEDIUM

A 27-year-old woman comes to the clinic because of progressive fatigue and muscle cramps for 2 months. She has had intermittent palpitations and lightheadedness. She takes no medications. She reports long-standing cravings for salty foods. Blood pressure is 92/58 mm Hg and pulse is 104/min. Physical examination shows diffuse hyperpigmentation of the palmar creases. Laboratory studies show: Na+ 128 mEq/L, K+ 5.8 mEq/L, HCO3− 18 mEq/L, glucose 62 mg/dL. Urine pH is 5.0. Which of the following is the most likely change in renal tubular function responsible for her acid–base abnormality?

Primary adrenal insufficiency causes low aldosterone, leading to decreased ENaC-mediated Na+ reabsorption and reduced lumen-negative potential, which decreases distal H+ and K+ secretion, producing a non–anion gap metabolic acidosis with hyperkalemia. Decreased alpha-intercalated H+ secretion describes type 1 RTA, which typically has urine pH >5.5.

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