Your Stress Hormone Controller
ACTH is a hormone from your pituitary gland (brain) that tells your adrenal glands to produce cortisol. It's the boss telling the factory how much stress hormone to make. Measuring ACTH alongside cortisol reveals WHERE a problem is: if cortisol is high with high ACTH, the pituitary is overdriving (Cushing disease). If cortisol is high with LOW ACTH, the adrenals are acting on their own (adrenal tumor).
What is ACTH (Adrenocorticotropic Hormone)?
ACTH is a 39-amino acid peptide from anterior pituitary corticotroph cells. Secreted in pulsatile fashion with diurnal rhythm (peak 6-8 AM, nadir midnight). Must be drawn AM, on ice, and processed quickly (degrades rapidly). Always interpret WITH cortisol.
↑ What High ACTH (Adrenocorticotropic Hormone) Means
Pituitary is overproducing ACTH. Causes: Cushing disease (pituitary adenoma), ectopic ACTH (lung cancer), or Addison disease (adrenals failing → pituitary compensates by making more ACTH).
Common symptoms:
If Cushing: weight gain (central), moon face, buffalo hump, striae, easy bruising, hypertension, diabetes · If Addison (compensatory high ACTH): fatigue, hyperpigmentation, salt craving
↓ What Low ACTH (Adrenocorticotropic Hormone) Means
Pituitary isn't making enough ACTH. Causes: exogenous steroid use (most common—suppresses pituitary), pituitary failure (hypopituitarism), or adrenal tumor producing cortisol independently.
Common symptoms:
If adrenal insufficiency: fatigue, weight loss, hypotension, hyperpigmentation (Addison) · If pituitary failure: fatigue, loss of other pituitary hormones
Why It Matters
When normal:
Distinguishes ACTH-dependent from ACTH-independent Cushing syndrome
Identifies pituitary vs adrenal cause of cortisol abnormalities
Diagnoses secondary adrenal insufficiency
Risks if abnormal:
High ACTH + high cortisol: Cushing disease or ectopic ACTH
Low ACTH + high cortisol: adrenal tumor
High ACTH + low cortisol: primary adrenal insufficiency (Addison)
What Can Cause Abnormal Levels?
Cushing Disease (pituitary adenoma)
35% likelyACTH-secreting pituitary tumor drives cortisol overproduction. Most common cause of endogenous Cushing syndrome.
Adrenal Insufficiency (Addison)
30% likelyAdrenals can't produce cortisol → pituitary compensates by increasing ACTH.
Exogenous Steroids (low ACTH)
Prednisone and other steroids suppress pituitary ACTH. Most common cause of low ACTH.
Ectopic ACTH (lung cancer)
Small cell lung cancer or carcinoid tumors can produce ACTH.
Stress
Acute illness, surgery, and stress physiologically elevate ACTH and cortisol.
What You Can Do
Always measure ACTH with cortisol (they're meaningless alone)
Impact: The pair reveals the diagnosis \u00B7 Timeline: Same draw, AM
Draw at 8 AM (ACTH has strong diurnal rhythm)
Impact: AM sample is the standard \u00B7 Timeline: Morning
If lifestyle changes aren't enough:
If Cushing suspected: 24h urine cortisol, late-night salivary cortisol, dexamethasone suppression test
Impact: Confirms hypercortisolism before localizing \u00B7 Timeline: Per endocrinology
Recommended retest: Per endocrinology evaluation; stimulation tests for adrenal insufficiency
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