These pituitary tumors make a hormone called adrenocorticotropic hormone (ACTH), which stimulates the adrenal glands to make proteins called glucocorticoids. When the body makes too much ACTH, it causes a disorder known as Cushing's disease. Most patients who develop this disorder are women in their 30s and 40s. ACTH-producing tumors account for 10 to 15 percent of pituitary tumors.
Symptoms
Patients with Cushing's disease may experience unexplained weight gain, diabetes, increased blood pressure, easy bruising, moodiness or depression, and irregular or absent menstrual periods.
Diagnosis
Cushing's disease must be distinguished from several other diseases that can increase the production of hormones from the adrenal glands. Cushing's disease is diagnosed using blood tests that look for abnormal secretion of a hormone called cortisol. MRI may also be employed, but sometimes a pituitary tumor that causes Cushing's disease is so small that it may not be visible using this imaging test.
If the tumor cannot be seen on MRI or if the diagnosis is uncertain, a test called petrosal venous sampling may be necessary. This is a procedure during which a sample of blood is taken from the petrosal sinuses -- which drain the pituitary gland on both sides -- and checked for elevated cortisol levels. A higher than normal amount of a cortisol is a sign of Cushing's disease.
The test can also help locate the tumor within the pituitary gland, if the cortisol level is found to be higher on one side compared to the other.
Treatment
Surgery to remove the tumor is the primary therapy for Cushing's disease. Surgery for pituitary tumors is often performed through a minimally invasive approach called transphenoidal transnasal resection, whereby the surgeon removes the tumor through an incision in the nasal passage. In cases where the tumor is too large to be removed through this approach, the surgeon performs a craniotomy, removing the tumor through an incision in the front of the skull.
If surgery alone is not curative, medical treatment with a drug such as ketoconazole (Nizoral®) is used. In rare cases, when even this approach is not effective, the adrenal glands may be surgically removed.
Radiation therapy -- radiosurgery and intensity-modulated radiation treatment (IMRT) -- may also be used to treat these tumors. Radiosurgery, or stereotaxic radiosurgery, is a type of external radiation therapy that uses special equipment to give a single large dose of radiation to a tumor. IMRT uses radiation beams of varying intensity created to match specific tumor angles and shapes so that the tumor is targeted as precisely and uniformly as possible. This helps to reduce the damage to delicate structures in the area, such as the optic nerves.
Follow-Up
Your doctor will see you periodically and perform certain tests to ensure that your pituitary tumor has not returned. If medication is part of your treatment, you may need to take it for the rest of your life to prevent tumor recurrence.
