Also known as: ACTH, Adrenal Corticotropin, Corticotropin

This is a test ordered when a patient has signs or symptoms associated with excess or deficient cortisol. Measuring both the ACTH and cortisol levels 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, health professionals can learn much by identifying an imbalance in this relationship and the direction in which the imbalance occurs.

Too much cortisol will often cause symptoms weight issues 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 findings including high blood pressure, low potassium, high bicarbonate, and high glucose (or even diabetes). Patients with insufficient cortisol production may exhibit symptoms including muscle weakness, fatigue, weight loss, increased skin pigmentation (even in areas not exposed to the sun), and loss of appetite. This is often accompanied by findings including low blood pressure, low blood glucose, low sodium, high potassium, and high calcium.

Symptoms suggestive of hypopituitarism include loss of appetite, fatigue, hypogonadism, irregular menstrual cycle, decreased sex drive, frequent nighttime urination, and weight loss. When the condition is due to a (usually benign) pituitary tumor, the patient may also have symptoms associated with the compression of nearby cells and nerves. The tumor may 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.