Adrenocorticotropic hormone (ACTH)
Also called: ACTH, Adrenocorticotropic hormone, Corticotropin
The pituitary hormone that tells the adrenal glands to make cortisol. Measured together with cortisol, it is the test that separates a pituitary or adrenal problem — the key to working up both cortisol excess (Cushing's) and cortisol deficiency (Addison's).
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What does Adrenocorticotropic hormone (ACTH) measure?
ACTH is made by the pituitary gland and drives the adrenal glands to produce cortisol, the main stress hormone. The two work in a feedback loop, so ACTH is only meaningful when read together with a cortisol drawn at the same time — the combination localises where a problem sits. It follows a strong daily rhythm, peaking on waking and falling overnight, so timing matters. Its role is to pinpoint the source of an adrenal problem already suspected from cortisol testing: in cortisol excess, whether the drive is coming from the pituitary, an ectopic tumour, or the adrenal itself; in cortisol deficiency, whether the adrenal has failed (ACTH high) or the pituitary has (ACTH low).
What does a high Adrenocorticotropic hormone (ACTH) level mean?
- With high cortisol — Cushing's disease (a pituitary ACTH-secreting tumour) or an ectopic ACTH-producing tumour.
- With low cortisol — primary adrenal insufficiency (Addison's disease); the pituitary pushes ACTH up trying to stimulate failing adrenals.
- Congenital adrenal hyperplasia — an enzyme block raises ACTH drive.
What does a low Adrenocorticotropic hormone (ACTH) level mean?
- With high cortisol — an adrenal tumour making cortisol directly, which suppresses pituitary ACTH.
- With low cortisol — secondary adrenal insufficiency: the pituitary or hypothalamus is under-driving the adrenals, most commonly after long-term steroid medication suppresses the axis.
- Exogenous steroid use.
When to discuss with a doctor
ACTH is never read alone — always with a same-time cortisol, because it is the pair that tells the story. It is the second step once cortisol testing suggests either Cushing's syndrome (too much cortisol) or adrenal insufficiency (too little), and it directs the search to the pituitary versus the adrenal. New adrenal insufficiency — fatigue, weight loss, low blood pressure, low sodium, high potassium, skin darkening — can be dangerous and needs prompt endocrine assessment, as can a suspected adrenal crisis (an emergency). Mediora.AI shows ACTH beside cortisol and the electrolyte pattern so the axis can be read together; the diagnosis and imaging belong with endocrinology.
Related markers
Commonly confused with
- Cortisol Cause and effect on the same form. ACTH is the pituitary's instruction; cortisol is what the adrenal glands produce in response. Reading them together is what shows where a problem sits - above or below.