ACTH levels in the blood are measured to help detect, diagnose, and monitor conditions associated with excessive or deficient cortisol in the body. These conditions include:
Cushing disease: excess cortisol that is due to an ACTH-producing tumor in the pituitary gland (usually a benign tumor)
Cushing syndrome: refers to the symptoms and signs associated with excess cortisol. In addition to Cushing disease, Cushing syndrome may be due to an adrenal tumor, adrenal hyperplasia, the use of steroid medications, or due to an ACTH-producing tumor located outside the pituitary (ectopic), such as in the lungs.
Addison disease, also called primary adrenal insufficiency: decreased cortisol production due to adrenal gland damage
Secondary adrenal insufficiency: decreased cortisol production because of pituitary dysfunction
Hypopituitarism: pituitary dysfunction or damage that leads to decreased (or no) hormone production by the pituitary, including ACTH production
Measuring both ACTH and cortisol can help to differentiate among some of these conditions because the level of ACTH normally changes in the opposite direction to the level of cortisol.
People with insufficient cortisol production may exhibit symptoms such as:
Increased skin pigmentation, even in areas not exposed to the sun
Loss of appetite
These are often accompanied by findings such as low blood pressure, low blood glucose, low sodium, high potassium, and high calcium.
Symptoms suggestive of hypopituitarism include loss of appetite, fatigue, irregular menstrual cycle, hypogonadism, decreased sex drive, frequent nighttime urination, and weight loss. When the condition is due to a pituitary tumor (usually benign), the affected person may also have symptoms associated with the compression of nearby cells and nerves. The tumor can affect the nerves controlling vision, causing symptoms such as "tunnel vision" (inability to see things off to the side), loss of vision to some localized areas, or double vision, and can cause a change in a pattern of headaches.
In many cases, the interpretation of the results can be complex. Levels of both ACTH and cortisol vary throughout the day. Normally, ACTH will be at its highest level in the morning and lowest at night. It will stimulate cortisol production, which will follow the same daily pattern but will rise after ACTH does and fall to its lowest level very late in the evening. Conditions that affect the production of ACTH and cortisol often disrupt this diurnal variation.
Results of ACTH and cortisol tests are often evaluated together. The table below indicates the common patterns of ACTH and cortisol seen with different diseases involving the adrenal and pituitary glands.
Cushing disease (pituitary tumor producing ACTH)
"Ectopic" ACTH (ACTH made by a tumor outside the pituitary, usually in the lung)
An increased ACTH result can mean that a person has Cushing disease, Addison disease, or ectopic ACTH-producing tumors. A decreased ACTH result can be due to an adrenal tumor, steroid medication, or hypopituitarism.
It is impossible to reliably distinguish Cushing disease and ectopic ACTH from cortisol and ACTH measurement alone. A variety of other tests, including dexamethasone suppression and inferior petrosal sinus blood collection, are often used to assist health practitioners in making this distinction.
If an abnormal level of ACTH and/or cortisol is detected, a health practitioner will do additional testing to help confirm the findings and to help determine its cause. Testing the change in the level of cortisol when certain drugs are given to stimulate or suppress hormone production often helps the health care provider make the right diagnosis.
If the findings of the initial tests indicate insufficient cortisol production, a health practitioner may order an ACTH stimulation test. This test involves measuring the concentration of cortisol in a person's blood before and after an injection of synthetic ACTH. If the adrenal glands are functioning normally, then cortisol levels will rise with the ACTH stimulation. If cortisol levels don't rise, it indicates adrenal failure as can occur in Addison disease or hypopituitarism.
If a person has a high cortisol level, a health practitioner may perform a dexamethasone suppression test to help determine whether the cause is related to excess ACTH production by the pituitary. This test involves analyzing a baseline sample for cortisol, then giving the person a high dose of oral dexamethasone (a synthetic glucocorticoid) and measuring cortisol levels in subsequent timed samples. Dexamethasone suppresses ACTH production and should decrease cortisol production if the source of the excess is pituitary-related.
This article was last reviewed on January 10, 2013. | This article was last modified on August 7, 2014.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
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