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ACTH Testing...

http://www.labtestsonline.org/understanding/analytes/acth/test.html

Also known as: Corticotropin
Formally known as: Adrenocorticotropic hormone
Related tests: Cortisol; cortrosyn (ACTH) stimulation test; dexamethasone suppression test

How is it used?
When is it ordered?
What does the test result mean?
Is there anything else I should know?

How is it used?

ACTH levels in the blood are tested to help diagnose Cushing's syndrome, Addison's disease, and tumors of the pituitary and adrenal glands. 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, your doctor can learn much by identifying an imbalance in this relationship and the direction in which the imbalance occurs. For example, if your cortisol level is high and your ACTH level is also increased, that would indicate that there is a pituitary disease that causes production of too much ACTH.

The table below indicates the common patterns of ACTH and cortisol in different diseases involving the adrenal and pituitary glands.

Disease	Cortisol	ACTH
Cushing's disease (pituitary tumor making ACTH)	High	High
Adrenal tumor	High	Low
"Ectopic" ACTH (ACTH made by a tumor outside the pituitary, usually in the lung)	High	High
Addison's disease (adrenal damage)	Low	High
Hypopituitarism	Low	Low

When is it ordered?

This test is ordered when a patient has signs or symptoms of certain diseases, including Cushing's syndrome or Addison's disease.

Cushing's syndrome, caused by too much cortisol, often causes symptoms such as obesity (especially if it spares the arms and legs), a rounded face, fragile and thin skin, purple lines on the abdomen, muscle weakness, acne, and increased body hair. It is often accompanied by physical and laboratory signs, including high blood pressure, low potassium, high bicarbonate, and high glucose (or even diabetes). Cushing's disease refers to Cushing's syndrome due to a tumor in the pituitary that makes ACTH. Other causes of Cushing's syndrome include adrenal tumors that make cortisol, tumors in other parts of the body (usually the lungs) that make ACTH, and taking high dose steroids prescribed by your doctor.

Addison's disease presents with symptoms such as muscle weakness, fatigue, weight loss, increased skin pigmentation (even in areas not exposed to the sun) and loss of appetite, often accompanied by laboratory and physical signs such as low blood pressure, low blood glucose, low sodium, high potassium, and high calcium.

Findings suggestive of hypopituitarism (usually due to a benign tumor that reduces pituitary gland secretion) include loss of appetite, fatigue, irregular menstrual cycle, hypogonadism (lower levels of sex hormones), decreased sex drive, frequent nighttime urination, and weight loss. The tumors can also block 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, and double vision, and can cause a change in pattern of headaches.

What does the test result mean?

ACTH is usually ordered if you are found to have low cortisol or have signs or symptoms that suggest adrenal or pituitary disease. Changes in ACTH and cortisol are usually evaluated together, as shown in the table above.

An increased ACTH result can mean that a patient has Cushing's disease, Addison's disease, or ectopic ACTH-producing tumors or pituitary growths. A decreased ACTH result can mean an adrenal tumor that is making cortisol or hypopituitarism.

In some cases, the test results are not clear enough to interpret. Testing the change in ACTH and/or cortisol when certain drugs are given often helps to clarify the picture and allows the doctor to make the right diagnosis. The most commonly used drugs are cortrosyn (cosyntropin, a drug form of ACTH) and dexamethasone.

• Cortrosyn, like ACTH, should normally tell the adrenal glands to make cortisol. If cortisol levels don't rise after cortrosyn is given, this indicates adrenal failure as can occur in Addison's disease or hypopituitarism.
• Dexamethasone is a very potent drug that acts like cortisol. In normal people, it should stop ACTH production. By testing the ability of different doses of dexamethasone to stop ACTH production, it is often possible to tell if the patient has Cushing's syndrome and help determine its cause.

A number of other drugs are sometimes used, including insulin, corticotropin releasing hormone, and metyrapone (metapyrone).

PLEASE NOTE: Numerically reported test results are interpreted according to the test's reference range, which may vary by the patient's age, sex, as well as the instrumentation or kit used to perform the test. A specific result within the reference (normal) range – for any test – does not ensure health just as a result outside the reference range may not indicate disease. To learn more about reference ranges, please see the article, Reference Ranges and What They Mean. To learn the reference range for your test, consult your doctor or laboratorian. Lab Tests Online recommends you consult your physician to discuss your test results as a part of a complete medical examination.

Is there anything else I should know?

Some drugs and conditions can cause ACTH levels to rise, including amphetamines, insulin, levodopa, metoclopramide, and RU 486.

Drugs that cause ACTH to fall include dexamethasone and other drugs that act like cortisol (including prednisone, hydrocortisone, prednisolone, and methylprednisolone), and megestrol acetate.

Concentration of ACTH varies greatly at different times of the day, with the highest amount registered about 8 am and the lowest about midnight. Theses changes make it hard to evaluate ACTH production when cortisol levels are normal or only slightly abnormal. However, when cortisol levels are clearly abnormal, there is no special preparation needed for the test.

Secretion of ACTH may be increased by stress.

ACTH has also been used as a drug to treat Multiple Sclerosis.