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Diagnostic Tests — Adrenal & Cortisol Disorders
ACTH (Cosyntropin) Stimulation Test
What is this test?
- Evaluates adrenal cortex function
- Best initial diagnostic test for adrenal insufficiency
- Procedure:
- Measure baseline serum cortisol
- Administer cosyntropin (synthetic ACTH)
- Recheck cortisol at 30–60 minute
- Cortisol rises → adrenal glands functioning
- Cortisol does NOT rise → primary adrenal insufficiency (Addison disease)
When do you answer ACTH (Cosyntropin) Stimulation Test?
Chronic presentation (Addison disease):
- Fatigue, weakness
- Weight loss
- Hypotension
- Skin hyperpigmentation
- Hyponatremia
- Hyperkalemia
- Mild metabolic acidosis
- Salt craving (e.g., pickle juice)
→ Answer: ACTH stimulation test
Acute / ICU presentation:
- Unexplained hypotension
- Refractory to fluids or pressors
- History of chronic steroid use, autoimmune disease, or severe illness
→ Answer: ACTH stimulation test
Rapid Test Choice Guide
- Fatigue + hypotension + hyperpigmentation
- Hyperkalemia
- Hyponatremia
- Salt craving
→ ACTH (cosyntropin) stimulation test
- ICU patient with unexplained hypotension
→ ACTH (cosyntropin) stimulation test - Truncal (central) obesity
- Moon face
- Buffalo hump
- Purple striae
- Easy bruising
→ 24-hour urinary free cortisol
(or overnight dexamethasone suppression test)
-
- Low energy + dark skin + high K⁺ = ACTH stimulation test
- Central obesity + striae = urinary cortisol
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