Cushing disease vs Cushing syndrome from ectopic or adrenal sources
How to tell Cushing disease and Cushing syndrome from ectopic or adrenal sources apart when a board question makes them look alike.
Disease means pituitary ACTH; ectopic ACTH is ACTH-high but usually nonsuppressible; adrenal Cushing has high cortisol with suppressed ACTH.
Side by side
Pituitary ACTH adenoma causing cortisol excess with ACTH-dependent labs and partial suppression on high-dose dexamethasone or CRH response.
Ectopic ACTH causes severe ACTH-dependent cortisol excess without pituitary feedback response; adrenal cortisol tumors suppress ACTH.
Pituitary corticotroph adenoma secretes ACTH but often keeps enough feedback biology to respond to high-dose dexamethasone or CRH testing.
Ectopic tumors secrete ACTH outside pituitary control; adrenal tumors secrete cortisol autonomously and shut down pituitary ACTH. Bronchial carcinoid ectopic ACTH can occasionally suppress on high-dose dexamethasone, mimicking pituitary disease.
High cortisol, high ACTH, pituitary lesion, CRH response, or high-dose dexamethasone suppression supports Cushing disease.
Very high ACTH without suppression suggests ectopic ACTH; high cortisol with low ACTH suggests adrenal cortisol source.
The trap
Cushing syndrome names the cortisol phenotype, while Cushing disease names the pituitary ACTH cause.
The repair move
For cortisol excess, name the phenotype first, then split ACTH-low adrenal from ACTH-high pituitary or ectopic disease.
Try a free question
CoreA patient has central obesity, purple abdominal striae, proximal muscle weakness, high cortisol, high ACTH, and cortisol suppression after high-dose dexamethasone. Which diagnosis best fits?
Show answer and explanation
Answer: A. Cushing disease. ACTH-dependent cortisol excess with high-dose dexamethasone suppression supports pituitary Cushing disease.
Why the other choices are tempting
- B. Ectopic ACTH is ACTH-dependent but typically does not suppress like pituitary disease.
- C. Adrenal cortisol adenoma should suppress ACTH.
- D. Primary adrenal insufficiency causes low cortisol with high ACTH.
- E. Conn syndrome causes aldosterone excess, not cortisol excess.
Flashcards
Tap a card to flip it.
What does Cushing disease specifically mean?
Cushing disease means pituitary ACTH-driven cortisol excess.
What ACTH pattern points to an adrenal cortisol tumor?
High cortisol with low ACTH points to an ACTH-independent adrenal source.
Quick answers
What is the fastest way to tell Cushing disease from Cushing syndrome from ectopic or adrenal sources?
Disease means pituitary ACTH; ectopic ACTH is ACTH-high but usually nonsuppressible; adrenal Cushing has high cortisol with suppressed ACTH.
What is the key clue for Cushing disease?
Pituitary ACTH adenoma causing cortisol excess with ACTH-dependent labs and partial suppression on high-dose dexamethasone or CRH response.
What is the key clue for Cushing syndrome from ectopic or adrenal sources?
Ectopic ACTH causes severe ACTH-dependent cortisol excess without pituitary feedback response; adrenal cortisol tumors suppress ACTH.
What is the common trap with Cushing disease vs Cushing syndrome from ectopic or adrenal sources?
Cushing syndrome names the cortisol phenotype, while Cushing disease names the pituitary ACTH cause.