Adrenocorticotropic Hormone (ACTH)

Hormones marker

ACTH

Adrenocorticotropic Hormone (ACTH)

Category: Hormones
Unit: pmol/L

Pituitary hormone that drives cortisol production by the adrenal cortex. Interpreted alongside cortisol to evaluate the hypothalamic-pituitary-adrenal (HPA) axis. Follows a diurnal rhythm, highest in the early morning.

PED Notes

Directly relevant after any glucocorticoid use. Exogenous glucocorticoids (oral, injected, or even high-dose inhaled/topical) suppress ACTH and can cause adrenal suppression that persists for weeks to months after stopping. Athletes who run prednisone, dexamethasone, or frequent corticosteroid joint injections, or who use compounds with HPA-suppressing effects, can present with fatigue and low cortisol once the steroid is withdrawn. Pair ACTH with cortisol: low cortisol with low or inappropriately normal ACTH points to secondary or tertiary (pituitary/hypothalamic) adrenal insufficiency, while low cortisol with high ACTH points to primary adrenal failure (Addison's). Collect in the early morning.

When high

When HIGH:

  • High ACTH with low cortisol indicates primary adrenal insufficiency (Addison's disease): the pituitary is driving hard but the adrenals cannot respond. This is a medical condition requiring endocrinology and glucocorticoid replacement
  • High ACTH with high cortisol can indicate ACTH-dependent Cushing's (pituitary adenoma or ectopic ACTH); needs specialist work-up
  • Markedly raised ACTH should never be self-managed; refer for medical evaluation

When low

When LOW:

  • Low ACTH with low cortisol indicates secondary or tertiary adrenal insufficiency, most commonly from suppression by exogenous glucocorticoids (prednisone, dexamethasone, repeated corticosteroid injections) or, less commonly, pituitary disease
  • This is the pattern to watch for after a course of steroids: the HPA axis is suppressed and recovery can take weeks to months. Do not stop glucocorticoids abruptly; taper under medical supervision
  • A morning cortisol can be used to confirm HPA recovery (a morning cortisol above roughly 300 nmol/L generally indicates an intact axis); equivocal results warrant a stimulation test
  • Low ACTH with high cortisol suggests an autonomous adrenal source (adrenal Cushing's); refer

Clinical context:

  • ACTH is only interpretable alongside a paired cortisol drawn at the same time, ideally early morning
  • Sample handling matters: ACTH is labile and usually needs a chilled EDTA tube processed quickly, or the result reads falsely low
  • After significant glucocorticoid exposure, suspect adrenal suppression in any athlete with fatigue, low blood pressure, nausea, or poor stress tolerance, and involve a clinician

History Chart

Reading History

Frequently Asked Questions

Reference Ranges

Standard Range

1.6 - 13.9 pmol/L

VitalMetrics Range

1.6 - 13.9 pmol/L

Statistics