Ectopic Cushing’s syndrome

Definition

Ectopic Cushing's syndrome is a condition caused by an ACTH-secreting tumor outside the pituitary or adrenal glands.

Causes, incidence, and risk factors

Cushing's syndrome is the result of excess glucocorticoid hormones secreted over a long period of time. About 15% of Cushing's syndrome cases are due to ectopic Cushing's syndrome.

Ectopic Cushing's syndrome is caused by tumors that secrete adrenocorticotropic hormone (ACTH). Other causes of Cushing's syndrome are oversecretion of ACTH by the pituitary gland, a tumor of the adrenal gland, or long-term administration of corticosteroid drugs commonly used to treat conditions such as rheumatoid arthritis and asthma.

Small cell tumors of the lung, tumors of the thymus gland, islet cell tumors of the pancreas, and medullary carcinoma of the thyroid are tumors that can secrete ACTH, although this occurs rarely.

Symptoms

Ectopic Cushing's syndrome tends to present with less dramatic features than classic Cushing's syndrome, but with higher blood pressure and lower potassium. Weight loss may be present due to underlying cancer.

Classic features of Cushing's syndrome are:

• moon face (round, red, and full)
• "buffalo hump" -- collection of fat between the shoulders
• central obesity -- protruding abdomen and thin extremities
• weakness
• headache
• acne or superficial skin infections
• thirst
• increased urination
• purple striations on the skin of the abdomen, thighs, and breasts
• mental changes
• impotence or cessation of menses (loss of menstrual periods)

Signs and tests

Tests are done to confirm hypercortisolism, then further tests are done to determine the cause.

Tests that confirm hypercortisolism:

• a 24-hour urine for cortisol and creatinine
• a dexamethasone suppression test
• serial serum cortisol levels

• serum ACTH, elevated

• fasting glucose, elevated
• serum potassium, low

Treatment

The best treatment for ectopic Cushing's syndrome is surgical removal of the tumor. This is usually possible when the tumor is benign (noncancerous).

However, many tumors are malignant (cancerous), and have metastasized (spread to other areas of the body) before cortisol excess has been diagnosed,. Surgical removal is not possible in these situations, and drugs to suppress cortisol secretion may be given. They include: ketoconazole, aminoglutethimide, and metyrapone.

Expectations (prognosis)

Surgical removal of the tumor may lead to full recovery, but there is a chance of the tumor coming back. Survival for people with ectopic tumors depends upon the outcome associated with the particular tumor type.

Complications

• the tumor may spread
• excess cortisol may continue

Calling your health care provider

Call your health care provider if symptoms of Cushing's syndrome appear.

Prevention

Prompt treatment of tumors may reduce the risk in some cases. Many cases are not preventable.

Illustrations

Endocrine glands

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Cushing's syndrome - ectopic