Type of test :

Blood

Normal findings

 Adult/elderly:

 Female: 19 years and older: 6-58 pg/mL

 Male: 19 years and older: 7-69 pg/mL

 Children:

 Male and female: 10-18 years: 6-55 pg/mL

 Male and female: 1 week-9 years: 5-46 pg/mL

Test explanation and related physiology

The ACTH tests the anterior pituitary gland function and provides the greatest insight into the causes of either Cushing syndrome (overproduction of cortisol) or Addison disease (underproduction of cortisol). An elaborate feedback mechanism for cortisol exists to coordinate the function of the hypothalamus, pituitary gland, and adrenal glands. ACTH is an important part of this mechanism. Corticotropin-releasing hormone (CRH) is made in the hypothalamus. This stimulates ACTH production in the anterior pituitary gland. This, in turn, stimulates the adrenal cortex to produce cortisol. The rising levels of cortisol act as negative feedback and curtail further production of CRH and ACTH .

In a patient with Cushing syndrome, an elevated ACTH level can be caused by a pituitary or a nonpituitary (ectopic) ACTH producing tumor, usually in the lung, pancreas, thymus, or ovary. ACTH levels over 200 pg/mL usually indicate ectopic ACTH production. If the ACTH level is lower than normal in a patient with Cushing syndrome, an adrenal adenoma or carcinoma is probably the cause of the hyperfunction.

In patients with Addison disease, an elevated ACTH level indicates primary adrenal gland failure, as in adrenal gland destruction caused by infarction, hemorrhage, or autoimmunity; surgical removal of the adrenal gland; congenital enzyme deficiency; or adrenal suppression after prolonged ingestion of exogenous steroids. If the ACTH level is lower than normal in a patient with adrenal insufficiency, hypopituitarism is most prob ably the cause of the hypofunction.

One must be aware that there is a diurnal variation of ACTH levels that corresponds to variation of cortisol levels. Levels in evening (8 pm to 10 pm) samples are usually one-half to two- thirds those of morning (4 am to 8 am) specimens. This diurnal variation is lost when disease (especially neoplasm) affects the pituitary or adrenal glands. Likewise, stress can blunt or eliminate this normal diurnal variation.

Interfering factors

 • Stress (trauma, pyrogens, or hypoglycemia) and pregnancy can increase levels.

 • Recently administered radioisotope scans can affect levels.

* Drugs that may cause increased ACTH levels include amino glutethimide, amphetamines, estrogens, ethanol, insulin, metyrapone, spironolactone, and vasopressin.

* Corticosteroids may decrease ACTH levels.

 Procedure and patient care

 • See inside front cover for Routine Blood Testing.

 • Fasting: yes

 • Blood tube commonly used: green

 • Evaluate the patient for stress factors that could invalidate the test results.

 • Evaluate the patient for sleep pattern abnormalities. With a normal sleep pattern, the ACTH level is the highest between 4 am and 8 am and the lowest around 9 pm.

 • Chill the blood tube to prevent enzymatic degradation of ACTH.

 • Place the specimen in ice water and send it to the chemistry laboratory immediately. ACTH is a very unstable peptide in plasma and should be stored at −20° C to prevent artificially low values.

Abnormal findings

 Increased levels

- Addison disease (primary adrenal insufficiency)

- Cushing syndrome (pituitary-dependent adrenal hyperplasia)

- Ectopic ACTH syndrome Stress

- Adrenogenital syndrome (congenital adrenal hyperplasia)

Decreased levels

 Secondary adrenal insufficiency (pituitary insufficiency)

- Cushing syndrome

- Hypopituitarism Adrenal adenoma or carcinoma

- Steroid administration