ACTH (Adreno Corticotrophic Hormone)

The ACTH (Adreno Corticotrophic Hormone) blood test measures adrenocorticotropic hormone, a peptide hormone produced by the anterior pituitary gland.

ACTH forms a central part of the hypothalamic-pituitary-adrenal, or HPA, axis. Signals from the hypothalamus stimulate the pituitary gland to release ACTH, which travels through the bloodstream to the adrenal glands and stimulates the adrenal cortex to produce cortisol.

The test contains 1 biomarker: ACTH (Adreno Corticotrophic Hormone).

ACTH is particularly useful when a cortisol result is abnormal or when a clinician is investigating possible adrenal insufficiency, pituitary dysfunction or a disorder associated with cortisol excess.

The relationship between ACTH and Cortisol is more informative than either measurement in isolation. For example, low cortisol accompanied by markedly raised ACTH can support primary adrenal insufficiency, where the adrenal glands are not responding appropriately. Low cortisol with low or inappropriately normal ACTH can instead raise concern about pituitary or hypothalamic dysfunction.

ACTH may also be measured after biochemical evidence of cortisol excess has already been established. In that setting, ACTH can help determine whether cortisol production is ACTH-dependent or ACTH-independent. It should not normally be used as a stand-alone screening test for Cushing syndrome.

Timing and sample handling are particularly important for this hormone. ACTH follows a strong daily rhythm and is usually assessed in the morning, often alongside a cortisol measurement. ACTH is also unstable after collection, so the blood sample requires specialist handling to preserve an accurate result.

London Blood Tests currently advises an expected turnaround of approximately 2 business days after the laboratory receives your correctly processed sample.

Your report is sent securely once laboratory analysis and authorisation are complete. The underlying specialist laboratory currently lists a 1-day analytical turnaround, but additional collection, transport and reporting time means the customer-facing London Blood Tests turnaround is approximately 2 business days.

An unsuitable sample, delayed processing or failure to meet the required temperature conditions may prevent reliable ACTH analysis and could require recollection.

Your laboratory report will show your ACTH (Adreno Corticotrophic Hormone) concentration together with the reference interval used by the analysing laboratory.

The result should rarely be interpreted by itself. The most useful interpretation usually comes from comparing ACTH with a cortisol measurement obtained at approximately the same time.

A pattern of low cortisol with markedly raised ACTH is consistent with the pituitary gland attempting to stimulate adrenal glands that are not producing enough cortisol. Where cortisol deficiency has been confirmed, this pattern can support primary adrenal insufficiency.

A pattern of low cortisol with low or inappropriately normal ACTH may suggest central adrenal insufficiency caused by pituitary or hypothalamic dysfunction. Further endocrine testing is usually required because a single ACTH result does not establish the diagnosis.

Where excessive cortisol production has already been confirmed using appropriate testing, a suppressed ACTH result can suggest that cortisol production may be occurring independently of pituitary ACTH, such as from an adrenal source.

Conversely, a normal or raised ACTH in confirmed hypercortisolism can indicate an ACTH-dependent process. Further investigation may then distinguish pituitary Cushing disease from ectopic ACTH production.

Importantly, ACTH alone should not be used to screen for Cushing syndrome. Initial investigations generally assess cortisol excess using tests such as late-night salivary cortisol, urinary free cortisol or dexamethasone suppression testing before ACTH is used to classify the cause.

ACTH also varies naturally throughout the day and can rise during physiological stress. Reference ranges therefore depend on collection time and laboratory methodology.

Pre-analytical handling is another major consideration. ACTH is an unstable peptide hormone, which is why inappropriate transport or delayed processing can produce misleading results.

An abnormal ACTH result should therefore be interpreted alongside Cortisol, symptoms, medication, collection time and, where appropriate, dynamic endocrine testing and imaging.

London Blood Tests provides the ACTH blood test in London for people requiring specialist assessment of pituitary-adrenal hormone signalling.

The test costs £239 and measures one biomarker: ACTH (Adreno Corticotrophic Hormone). It is most commonly used alongside Cortisol when investigating adrenal insufficiency or when determining the source of an already established cortisol abnormality.

Because ACTH is unstable after blood collection, this is not a routine sample that can be handled in the same way as every other blood test. Correct EDTA collection, chilling and rapid plasma processing are important for a reliable result.

For people searching for a private ACTH blood test in London, the collection location and timing should therefore be selected with the laboratory requirements in mind. Morning collection with a paired Cortisol measurement is commonly preferred when clinically appropriate.

An ACTH result is not a stand-alone diagnosis of Addison's disease, pituitary disease or Cushing syndrome. Further hormone testing, dynamic endocrine testing or imaging may be required depending on the ACTH-Cortisol pattern.