Cushing Syndrome
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Cushing syndrome is a hormonal disorder in which the body has been exposed to high levels of cortisol for a long period of time. Treatments are available and depend on the cause of this disorder. Possible treatments include surgery, radiation therapy, and medications.
Cortisol is a hormone naturally produced by the adrenal glands in response to stress; it fluctuates throughout the day according to the body’s circadian rhythm. Cortisol performs many essential functions, such as raising blood glucose, maintaining blood pressure, and suppressing inflammation. However, a chronic high level of cortisol has detrimental effects on the body and can lead to Cushing syndrome.
Although it is produced by the adrenal glands, cortisol is regulated by the pituitary gland in the brain. The pituitary secretes adrenocorticotropic hormone (ACTH), which travels to the adrenal glands and stimulates them to grow and produce cortisol. Too much ACTH can cause high levels of cortisol in the body and, in turn, Cushing syndrome.
Cushing syndrome is divided into two categories, according to the cause of the disorder:
- Exogenous Cushing syndrome is the classification when the source of excess cortisol is outside the body—namely, medications called glucocorticoids. Examples of glucocorticoid medications include prednisone, dexamethasone, and cortisone.
- Endogenous Cushing syndrome is the term used when the body itself produces excess cortisol. The underlying cause is known as either ACTH-dependent or ACTH-independent.
- ACTH-dependent refers to an overproduction of ACTH that leads to high levels of cortisol. Usually, the cause of this is a pituitary tumor secreting ACTH, but sometimes the tumor is outside of the pituitary—for instance in the lung, thymus, or thyroid.
- ACTH-independent refers to normal ACTH levels accompanied by high cortisol levels. Either overactive adrenal glands or an adrenal tumor secreting cortisol may cause this condition.
Most often, Cushing syndrome can be attributed to an exogenous source, that is, glucocorticoids. Rarely is Cushing syndrome caused by an endogenous source, that is, by a tumor or by overactive adrenal glands.
Symptoms
Individuals with Cushing syndrome may have a variety of symptoms, including:
- Weight gain on the face, abdomen, and neck and upper back
- Thin arms and legs
- Striae on shoulders, abdomen, thighs, and other areas
- Bruising easily
- Severe fatigue
- Muscle weakness
- Poor wound healing
- Polyuria
- Facial plethora
- Hypertension
- Hyperglycemia
Women may have scalp hair loss, hirsutism, infertility, and amenorrhea, and men may have reduced libido and impotence. Children may be obese and have short stature.
Diagnosis
Symptoms can often suggest a diagnosis of Cushing syndrome, but certain tests are required to provide a definitive diagnosis. The goal of testing is to identify high cortisol levels. Such tests include:
- Salivary cortisol levels—This test involves swabbing the mouth for saliva and then measuring the cortisol levels in that sample.
- 24-hour urine free cortisol—This test measures cortisol levels in the urine over the course of 24 hours.
- Dexamethasone suppression test—For this test, the patient takes a dexamethasone pill by mouth late at night, and then cortisol levels are measured in the morning to determine whether dexamethasone suppressed the production of cortisol.
In addition, a corticotropin-releasing hormone response test may be conducted to measure ACTH levels to determine whether the tumor is a pituitary tumor.
Imaging studies can be used to visualize organs, soft tissues, and tumors in the body and are key to detecting a tumor. Computed tomography (CT) scan of the abdomen may be performed to identify an adrenal tumor. To detect a pituitary tumor, magnetic resonance imaging (MRI) is often the study of choice, although CT scan can image the tumor too. MRI or CT scans may be performed with or without contrast enhancement.
Risk Factors
As noted above, Cushing syndrome is caused by prolonged high levels of cortisol. This can be the outcome of taking glucocorticoids, having overactive adrenal glands or having a pituitary tumor, adrenal tumor or other ACTH-producing tumor.
Individuals who are at risk for Cushing syndrome are those who take glucocorticoids. Individuals may be prescribed this medication if they have undergone an organ transplantation or have an inflammatory disease, such as asthma, rheumatoid arthritis, or inflammatory bowel disease.
Cushing syndrome can affect both males and females and can occur at any age, although middle age is most common. However, Cushing syndrome caused by a pituitary or adrenal tumor is five times more likely to occur among women than men and tends to arise between 25 and 40 years of age.
Cushing syndrome itself is not hereditary, but certain hereditary conditions, such as multiple endocrine neoplasia I and Carney complex, can increase a person’s risk for developing tumors throughout the body, including the pituitary or adrenal gland, which can lead to Cushing syndrome.
Treatments
At Columbia, our neurosurgeons use the most sophisticated surgical techniques to treat Cushing syndrome caused by a pituitary tumor, resulting in the best possible outcomes. (Other specialists can treat Cushing syndrome that is caused by other factors, such as an adrenal tumor or glucocorticoids.)
Treatment for pituitary tumor typically consists of surgery, radiation therapy, medication, or a combination.
Most patients undergo surgery to resect the pituitary tumor. The tumor can be surgically resected by traditional open surgery, in which a craniotomy is done, or by transsphenoidal surgery, a minimally invasive approach in which the neurosurgeon removes the tumor through the nose or mouth. The aim of surgery is always complete resection while also preserving brain function. If complete resection cannot be safely achieved, subtotal resection is the goal.
If a patient is not a suitable candidate for surgery or only subtotal resection is achieved, radiation therapy can be used to treat the tumor. Due to advances in technology, radiation can be precisely delivered as a high-energy beam in a noninvasive procedure called stereotactic radiosurgery.
Medications to suppress ACTH levels can be used in addition to or instead of pituitary tumor surgery, if patients are not suitable candidates for surgery.
If surgical removal of the pituitary tumor affects the production of any hormones by the pituitary, hormone replacement therapy can be prescribed to restore hormone levels.