Cushing's syndrome is a rare hormonal disorder that occurs when the body's tissues are exposed to excessive levels of the hormone cortisol for a long period of time. Cortisol is produced by the adrenal glands and helps the body respond to stress, such as surgery and illness, and recover from infections. The hormone also helps maintain blood pressure and cardiovascular function and regulate the metabolism of proteins, carbohydrates and fats.
Benign, or non-cancerous, tumors of the pituitary gland called pituitary adenomas that secrete excessive amounts of adrenocorticotrophic hormone (ACTH) cause an estimated 70 percent of Cushing's syndrome cases in adults and is referred to as Cushing's disease. Other causes include tumors of the adrenal glands, which are located above the kidneys, as well as tumors occurring elsewhere in the body, such as the lungs, that secrete ACTH. This condition is known as ectopic ACTH syndrome. Rarely, some people may have an inherited tendency to develop tumors of one or more endocrine glands that can lead to Cushing's syndrome.
Cushing's syndrome is relatively rare, each year affecting only about 10 to 15 out of every million people. It most commonly occurs in adults between 20 and 50 years of age, with women accounting for over 70 percent of those diagnosed.
Symptoms of Cushing's syndrome may include:
Diagnosis of Cushing's syndrome is based on a review of your medical history, physical examination and laboratory tests, which help to determine the presence of excess levels of cortisol. Often X-ray exams of the adrenal or pituitary glands are useful for locating tumors. In addition, comparison of old and recent photographs will often highlight the changes in facial and body appearance in patients who develop Cushing's syndrome. The first step in diagnosing Cushing's disease is to confirm the presence of excessive cortisol secretion. This diagnosis is most easily made by the following tests:
Low-dose dexamethasone suppression test that involves taking a small dose of a cortisol-like drug dexamethasone (1 mg) at 11 p.m. and having blood drawn for cortisol the following morning. Normal individuals typically have very low levels of cortisol in these samples, indicating that ACTH secretion is suppressed, while cortisol is readily detected and oftentimes is increased in patients with Cushing's disease.
24-hour urine collection to measure cortisol levels.
Treatment for Cushing's syndrome depends on the specific reason for cortisol excess and may include surgery, radiation, chemotherapy or the use of cortisol-inhibiting drugs.
Reviewed by health care specialists at UCSF Medical Center.
Endocrinology Clinic at Mount Zion
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