What is Cushing's Disease?

It is a specific type of Cushing's Syndrome caused by a pituitary tumor that makes too much ACTH, which signals the adrenal glands to overproduce cortisol.

Cushing's Disease vs. Cushing's Syndrome:

• Cushing's Syndrome: General term for too much cortisol (any cause).
• Cushing's Disease: Specifically a pituitary tumor causing it (~70% of Cushing's cases).

Symptoms:

Same as Cushing's Syndrome (moon face, buffalo hump, purple striae, muscle weakness, high blood pressure, diabetes).

Diagnosis (The Challenge):

Diagnosing Cushing's Disease is one of the hardest puzzles in endocrinology. Many tests are needed:

• Step 1: Prove Cushing's Syndrome exists (24-hr urine cortisol, late-night salivary cortisol, dexamethasone suppression test).
• Step 2: Find the source. High ACTH = pituitary or ectopic. Low ACTH = adrenal tumor.
• Step 3: High-Dose Dexamethasone Test or CRH Stimulation Test to confirm pituitary source.
• Step 4: Pituitary MRI (but 40% of tumors are too small to see!).
• Step 5: IPSS (Inferior Petrosal Sinus Sampling)—a catheter test to sample blood directly from the pituitary veins.

Treatment:

• Surgery: Transsphenoidal resection. Cure rate ~70-90% if successful.
• Medications: Pasireotide, Ketoconazole, Metyrapone (to lower cortisol).
• Radiation: If surgery fails.
• Bilateral Adrenalectomy: Last resort (but causes Nelson's Syndrome).