ADRENO CORTICOTROPHIC HORMONE (ACTH)

Adrenocorticotropic Hormone (ACTH), also called corticotropin, is a blood test that measures the amount of ACTH in plasma. ACTH is produced by the pituitary gland, a small gland located at the base of the brain. Its primary function is to stimulate the adrenal glands to produce cortisol, a hormone involved in the stress response, blood-pressure regulation, metabolism, inflammation control, and maintenance of blood glucose.

ACTH is usually evaluated together with a cortisol test because the relationship between the two results helps doctors determine whether abnormal cortisol production originates from the pituitary gland, adrenal glands, or another source. ACTH levels naturally change throughout the day and are generally highest in the early morning.

Benefits of the Test

• Measures the concentration of ACTH in plasma.
• Assesses communication between the pituitary and adrenal glands.
• Supports the investigation of abnormally high or low cortisol levels.
• Helps evaluate suspected adrenal insufficiency.
• Supports the diagnosis of Addison disease in an appropriate clinical setting.
• Helps investigate Cushing syndrome and Cushing disease.
• May assist in identifying pituitary or adrenal causes of hormone imbalance.
• Supports monitoring after treatment for selected endocrine disorders.
• Can be interpreted with cortisol and dynamic hormone tests.
• Provides laboratory information for endocrinology treatment planning.

Why Doctors Recommend This Test

Doctors may recommend ACTH testing when a patient has symptoms or laboratory findings suggesting excessive or insufficient cortisol production. These may include unexplained weight changes, muscle weakness, persistent fatigue, low or high blood pressure, skin changes, abnormal pigmentation, irregular menstrual cycles, increased thirst, mood changes, or electrolyte abnormalities.

The test may also be requested when cortisol results are abnormal, when a pituitary or adrenal disorder is suspected, or during follow-up after surgery, radiation therapy, or medical treatment for an endocrine condition.

Preparation Before Test

• The sample is usually collected in the early morning because ACTH follows a daily rhythm.
• Fasting may be advised when ACTH and cortisol are tested together.
• Follow the exact collection time recommended by your doctor.
• Avoid strenuous exercise before collection unless otherwise instructed.
• Try to remain calm because physical and emotional stress can affect ACTH levels.
• Inform your doctor about steroid medicines, hormone treatments, and all other medications.
• Do not stop corticosteroids or any prescribed medicine without medical advice.
• Inform the laboratory about recent illness, surgery, trauma, or sleep-cycle changes.
• ACTH requires careful sample collection, cooling, processing, and transportation.
• Follow any additional instructions provided for simultaneous cortisol testing.

Normal Reporting Time

The Adrenocorticotropic Hormone (ACTH) test generally requires specialised analysis and careful pre-analytical sample handling. Results are usually available within a few working days after sample receipt, processing, analysis, validation, and quality review. The exact reporting time may vary according to the testing schedule and laboratory workflow.

Who Should Take This Test?

This test may be recommended for:

• Patients with abnormal blood or urine cortisol results.
• Individuals with suspected adrenal insufficiency.
• Patients being evaluated for Addison disease.
• Individuals with signs or symptoms of Cushing syndrome.
• Patients with suspected pituitary-gland dysfunction.
• Individuals with unexplained weakness, fatigue, or weight changes.
• Patients with unusual skin darkening or pigmentation.
• Individuals with persistent high or low blood pressure.
• Patients undergoing follow-up for a diagnosed adrenal or pituitary disorder.
• People specifically advised to undergo ACTH testing by an endocrinologist.

Detailed Information

ACTH is a peptide hormone produced by corticotroph cells in the anterior pituitary gland. Its release is controlled by corticotropin-releasing hormone from the hypothalamus. ACTH travels through the bloodstream to the adrenal cortex, where it stimulates cortisol production.

Cortisol normally provides negative feedback to the hypothalamus and pituitary gland. When cortisol levels rise, ACTH production usually decreases. When cortisol levels fall, ACTH production generally increases. Disturbance anywhere in this regulatory pathway can produce abnormal hormone levels.

High ACTH with low cortisol may suggest primary adrenal insufficiency, in which the adrenal glands cannot produce adequate cortisol despite stimulation from the pituitary gland. Addison disease is one possible cause, although additional investigations are required to identify the underlying condition.

Low or inappropriately normal ACTH with low cortisol may indicate secondary or tertiary adrenal insufficiency related to pituitary or hypothalamic dysfunction. Long-term corticosteroid use can also suppress the hypothalamic-pituitary-adrenal axis and affect ACTH and cortisol production.

High ACTH with high cortisol may be associated with an ACTH-producing pituitary tumour, known as Cushing disease, or ectopic ACTH production by a tumour outside the pituitary gland. Low ACTH with high cortisol may suggest cortisol production by an adrenal tumour or adrenal hyperplasia.

An ACTH result alone cannot confirm a specific endocrine disorder. Doctors interpret it with cortisol levels, symptoms, medical history, physical examination, and imaging findings. Additional investigations may include an ACTH stimulation test, dexamethasone suppression test, corticotropin-releasing hormone test, urine-free cortisol, late-night salivary cortisol, pituitary MRI, or adrenal imaging.

ACTH secretion is pulsatile and follows a circadian rhythm. Concentrations are usually highest during the early morning and lowest around midnight. Shift work, disrupted sleep, acute illness, severe stress, and changes in routine may influence the result.

ACTH is unstable after blood collection. The sample is generally collected into a suitable EDTA tube, kept chilled, and separated promptly according to laboratory procedures. Delayed processing or improper temperature control may produce an inaccurately low result.

Corticosteroid medicines and certain other drugs may interfere with hormone production or test interpretation. Patients should provide a complete medication history but must not stop prescribed treatment unless specifically advised by their doctor.

Reference intervals vary according to the laboratory method and the time of sample collection. The result should always be interpreted using the reference range printed on the individual report.

At Focus Diagnostics, ACTH testing is performed using established laboratory methods, controlled sample-handling procedures, and quality-assurance standards to provide reliable results for endocrine evaluation.