Diabetes Mellitus USMLE Step 1 Practice Question
A 58-year-old woman abruptly discontinues high-dose prednisone used for autoimmune disease. She presents with fatigue, nausea, and abdominal pain. Vital signs show BP 88/54 mmHg, HR 102/min, RR 18/min, temp 37°C. Laboratory studies reveal cortisol 2 μg/dL (normal 10-20), ACTH 8 pg/mL (normal 7-46), potassium 4.2 mEq/L, and glucose 95 mg/dL. Which mechanism best explains her clinical presentation and preserved electrolyte homeostasis?
Answer choices
- APosterior pituitary failure increases mineralocorticoid release
- BZona glomerulosa is destroyed by autoimmune disease
- CAldosterone is primarily regulated by the renin angiotensin systemCorrect answer
- DCortisol directly inhibits renal potassium secretion
- ETSH excess compensates for loss of ACTH
- FACTH-independent adrenocorticotropic hormone production from ectopic sources maintains adrenal function
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.