ACTH

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's disease: excess cortisol that is due to an ACTH-producing tumor in the pituitary gland (usually a benign tumor)
• Cushing's syndrome: refers to the symptoms and signs associated with excess exposure to cortisol. In addition to Cushing's disease, Cushing's syndrome may be due to an adrenal tumor, adrenal hyperplasia, the use of steroid medications, or due to an ACTH-producing tumor that is ectopic, located outside the pituitary (such as in the lungs).
• Addison's disease, 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.

Too much cortisol can cause symptoms that include:

• obesity, with majority of the weight on the trunk of the body and not the arms and legs
• rounded face
• fragile and thin skin
• purple lines on the abdomen
• muscle weakness
• acne
• increased body hair

These are often accompanied by findings such as high blood pressure, low potassium, high bicarbonate, high glucose levels, and sometimes diabetes.

People with insufficient cortisol production may exhibit symptoms such as:

• muscle weakness
• fatigue
• weight loss
• 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, and double vision, and can cause a change in a pattern of headaches.

An increased ACTH result can mean that a patient has Cushing's disease, Addison's disease, or ectopic ACTH-producing tumors. A decreased ACTH result can be due to an adrenal tumor, steroid medication, or hypopituitarism.

In some cases, the interpretation of the results can be complex. Concentrations 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.

• Cortrosyn, like ACTH, stimulates 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 potent drug that acts like cortisol. Dexamethasone should stop ACTH production. By testing the ability of different doses of dexamethasone to stop ACTH production, a doctor can tell if the person has Cushing's syndrome and determine its cause.

A number of other drugs are sometimes used to stimulate or suppress cortisol production, including insulin, corticotropin releasing hormone, and metyrapone (metapyrone).

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.

Secretion of ACTH may be increased by stress.

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