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Friday, October 2, 2026
EndocrineEasy
A 28-year-old female has Cushing's syndrome confirmed biochemically (elevated midnight salivary cortisol × 2, 24h urine free cortisol 3× upper limit of normal (ULN)). She is on no exogenous steroids. Which of the following is the most appropriate next test to determine the cause?
ADexamethasone suppression test
BPlasma ACTH level
CAdrenal CT scan
DPituitary MRI scan
Reveal the answer & full explanation
Correct answer: B — Plasma ACTH level
ADexamethasone suppression test
BPlasma ACTH level✓
CAdrenal CT scan
DPituitary MRI scan
Why Plasma ACTH level is correct
Once Cushing's syndrome is biochemically confirmed, the next step is plasma adrenocorticotropic hormone (ACTH) to determine whether the cause is ACTH-dependent or ACTH-independent.
Elevated ACTH (>20 pg/mL) = ACTH-dependent → pituitary (Cushing's disease, 70%) or ectopic source (15%) → pituitary MRI → corticotropin-releasing hormone (CRH) stimulation test plus inferior petrosal sinus sampling if needed.
Why the others are wrong
Dexamethasone suppression test — this is a screening/confirmation test for the diagnosis of Cushing's syndrome, which has already been established biochemically here; it does not localize whether the source is adrenal, pituitary, or ectopic.
Adrenal CT scan — imaging is premature before ACTH is measured; ordering it first risks chasing incidental adrenal "incidentalomas" and misses ACTH-dependent (pituitary/ectopic) causes, so it is reserved for confirmed ACTH-independent disease.
Pituitary MRI scan — pituitary imaging is only indicated once ACTH is shown to be elevated (ACTH-dependent); obtaining it first is wasteful and misleading, as ~10% of normal people have nonfunctioning pituitary incidentalomas.
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What is the PANRE Question of the Day?
Every day, FirstPassPA publishes one free, board-style question modeled on the PANRE (Physician Assistant National Recertifying Exam) and PANCE. Each one is a clinical vignette with a single best answer and a full explanation — including why the other options are wrong — so a two-minute daily habit steadily builds the pattern recognition the boards reward.
Unlike most PANRE prep tools, our daily question is completely public — no email wall and no sign-up. It is the same question we post to our social channels and send to our daily email list, drawn from the same clinician-reviewed, blueprint-mapped bank behind the full FirstPassPA app.
How to use it
Read the vignette, commit to an answer before you reveal it, and then read the explanation even when you get the question right — the reasoning for the distractors is usually where the real learning is. Rotate through the daily questions to keep every organ system fresh, and when your exam date gets closer, layer in longer, blueprint-weighted question blocks in the app.
Yes. FirstPassPA publishes one free board-style question every day — the full vignette, the correct answer, and a complete explanation — with no email address or account required. A free 7-day trial unlocks the full 7,200+ question bank, all 7 EOR rotations, flashcards, and an AI tutor.
How is the Question of the Day chosen?
It is drawn from the same clinician-reviewed FirstPassPA bank the PANCE and PANRE draw from — mapped to the NCCPA blueprint and rotated across organ systems so you see a broad mix over time. It is the same question posted to our social channels and daily email.
Does the Question of the Day help for the PANCE too?
Yes. The PANCE and PANRE cover the same NCCPA content blueprint, so daily board-style practice builds the recall and reasoning both exams test. PA students can use the same daily habit.
How should I use a question of the day to study?
Attempt it before revealing the answer, then read the full explanation even when you get it right — the reasoning for why the distractors are wrong is where most of the learning is. Pair the daily habit with focused, blueprint-weighted question blocks as your exam date approaches.
Educational use only. This question is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants.