Cushing's syndrome is a metabolic disorder that can have several causes. In this case it is caused by excessive production of cortisol by a tumor of an adrenal gland.
Causes, incidence, and risk factors
Cushing's syndrome is caused by elevated levels of cortisol, a key glucocorticoid hormone, over an extended period of time. The growth of a tumor on one of the two adrenal glands causes about 15% of all cases of Cushing's syndrome. Adrenal tumors secrete cortisol and may be benign (noncancerous) or malignant (cancerous). Benign tumors that may cause Cushing's syndrme include adrenal adenomas or micronodular hyperplasia. Adrenal carcinomas are malignant tumors that may cause Cushing's syndrome. Other causes of Cushing's syndrome are secretion of ACTH by a pituitary tumor , by another organ ( ectopic Cushing's syndrome ), and regular use of corticosteroids such as prednisone, commonly used to treat chronic conditions such as rheumatoid arthritis and asthma . Although they may develop in anyone at any age, adrenal tumors are more common in adults -- 70% of all adrenal tumors occur in adults. They are found in women more often than men and are relatively rare, occuring in 6 out of every 1,000,000 people.
Signs and tests
Tests to confirm Cushing's syndrome:
24-hour urine sample to measure the following:
Urine cortisolUrine creatinineDexamethasone suppression testSerum cortisol levels Saliva cortisol levels Tests to determine cause:
ACTH (low normal or undetectable) High-dose dexamethasone suppression test Abdominal CT (may show adrenal mass) Other findings may include:
Elevated fasting glucose
Low serum potassium
Low bone density by dual X-ray absorptiometry (DEXA)
Elevated cholesterol
Treatment
Cushing's syndrome due to an adrenal tumor is treated by surgical removal of the tumor (which often includes removal of the gland as well). Glucocorticoid replacement therapy is usually required until the other adrenal gland recovers from surgery. Nine to 12 months of glucocorticoid therapy may be required. If surgery is not possible, particularly with cases of adrenal carcinoma, medications can suppress the secretion of cortisol:
Mitotane Ketoconazole Aminoglutethimide Metyrapone Radiation therapy is rarely effective in patients with adrenal carcinoma and is usually not appropriate for adrenal adenoma.
Expectations (prognosis)
Patients with adrenal adenoma who undergo surgery have an excellent prognosis. Surgery success rates are very high with this type of tumor. For adrenal carcinoma, surgery is sometimes not possible. When surgery is performed, it does not always cure the cancer. Survival time ranges from 14 to 36 months after diagnosis of adrenal carcinoma.
Complications
Adrenal carcinoma can result in metastasis (spread) of the tumor to the liver or lungs.
Calling your health care provider
Call your health care provider if you develop any symptoms of Cushing's syndrome.
Prevention
Use caution when taking corticosteroid medications. Appropriate treatment of adrenal tumors may reduce the risk of complications in some patients with tumor-related Cushing's syndrome.