Cushing's disease is a specific subtype of a more general condition known as Cushing's syndrome. Both disorders result in elevated levels of a hormone called cortisol, but Cushing's disease is notable for being related to a problem with the pituitary gland. Cortisol is a hormone that the body normally produces in response to stress and it has a potent effect on many tissues in the body,
Cause
Cushing's disease is the result of a tumor in the pituitary gland, the Mayo Clinic explains. The pituitary is a gland located at the base of the brain that makes a variety of hormones, including ACTH, also known as adrenocorticotropin hormone. ACTH is responsible for stimulating the adrenal glands to make the hormone cortisol. An ACTH-secreting tumor in the pituitary can cause the overproduction of cortisol, leading to the symptoms of Cushing's disease.
Symptoms
One of the main symptom's of Cushing's disease, Family Doctor notes, is changes in the skin and in fat deposition in the body. Patients with Cushing's disease often have an increase in abdominal fat and may also have fat deposits in the area between the shoulders, leading to a characteristic sign known as a buffalo hump. A round and puffy face is another common symptom. People with Cushing's also have thin and easily bruised skin as well as stretch marks that may occur on the thighs, breast, arms and abdomen. Elevated cortisol levels also can cause suppression of the immune system, making it more difficult for cuts to heal.
Hormonal Imbalance
Another effect of Cushing's disease relates to how excess cortisol affects other hormones in the body. Cushing's disease disrupts the normal balance of sex hormones, which can cause differing effects on men and women. Women will experience a surge in testosterone, which will cause them to grow more body hair and have a deepening voice. This excess testosterone will also cause the menstrual cycle to become irregular. Men will develop an increase in estrogen, which can cause impotence as well as a diminished libido.
Diagnosis
There are two blood tests for which Cushing's disease will produce characteristic results. Because Cushing's disease results in elevated cortisol levels, doctors will often test the urine collected from a patient over a 24-hour period to measure cortisol levels, Lab Tests Online explains. The second test, which distinguishes Cushing's disease from other conditions that cause high cortisol levels, is called a dexamethasone suppression test. With this test, the patient is given a synthetic corticosteroid called dexamethasone. Normally this will suppress the secretion of ACTH, which will in turn lower cortisol levels. Patients with Cushing's disease, however, will continue to have high ACTH and cortisol production.
Familial Cushing's
Most cases of Cushing's are not inherited, but in some cases a genetic mutation is responsible for the pituitary tumor, the National Institute of Diabetes and Digestive and Kidney Disorders explains. This genetic condition is known as multiple endocrine neoplasia type I, or MEN1. This disorder predisposes patients to develop tumors in several different hormone-producing glands; patients who have Cushing's disease as a result of MEN1 may also develop tumors in their thyroid and parathyroid glands.
