Pituitary-dependent Cushing’s disease (PDCD), or Cushing’s disease, is a form of Cushing’s syndrome, a set of symptoms indicating unusually high levels of the hormone cortisol in the body. Most cases of Cushing’s syndrome are caused by medication, but in Cushing’s disease, the excess cortisol is instead produced by the body itself.
Cushing’s disease occurs when a tumor develops in the pituitary gland, a small body at the base of the brain that regulates cortisol production. In most cases, these tumors are noncancerous and are sometimes called pituitary adenomas.
The pituitary tumor causes the gland to create an abnormally large amount of pituitary adrenocorticotropic hormone (ACTH). In turn, ACTH tells the body to produce more cortisol than is normally needed.
Cushing’s disease is a progressive condition, meaning it gets worse over time when untreated.
Cortisol is a hormone your body normally releases in response to stress, exercise, and waking up in the morning. The main jobs of cortisol in the body include:
- throttling or suppressing the immune system
- metabolizing fats and carbohydrates
- increasing blood sugar
In PDCD, with cortisol levels higher than they should be, the hormone’s attempts to do these same jobs in the body can, essentially, misfire. The resulting symptoms and physical signs of PDCD can include:
- rapid or excessive weight gain, particularly around the stomach
- thinning skin that bruises easily
- purple stretch marks
- muscle weakness
- depression and fatigue
- skin darkening or acne
PDCD can also manifest in the form of other hormone-related changes. People who menstruate may notice their period skipping or disappearing, and erectile dysfunction can be an indicator in people who have a penis.
Other common symptoms of PDCD are:
- easy bruising
- thinning of the skin
- muscle weakness
The cause of PDCD is a tumor of the pituitary gland. The tumor forces the pituitary gland to create a large amount of pituitary adrenocorticotropic hormone (ACTH). This oversupply of ACTH signals the adrenal gland to make too much cortisol.
Your doctor will be able to confirm PDCD by measuring the levels of ACTH and cortisol in your body.
Cortisol readings may differ throughout the day. To account for the differences, some tests may be performed multiple times in one day.
Cortisol levels can be measured either through a blood, or serum, test or through a salivary, or spit, test. In a salivary level test, cortisol levels are taken at four specific times during the day. You’ll be asked to provide salivary samples that are then sent out for analysis.
Your doctor may also want to use imaging techniques like MRI or CT scans to get a clearer picture of the tumor. This can help determine a course of action.
Treatment for Cushing’s disease focuses on stopping the overproduction of ACTH by the pituitary gland. Usually, this means surgically removing the tumor (via a transsphenoidal pituitary adenectomy). Sometimes, the entire gland must be removed.
Other less common methods used to treat PDCD include:
- adrenalectomy, the removal of one (unilateral) or both (bilateral) adrenal glands
- gamma knife radiosurgery (GK), where tiny radiation beams focus on the tumor to destroy it and not cause harm to the tissue around it
- pituitary-directed radiation, which is radiation therapy focused on the pituitary gland
After primary treatment, your doctor may prescribe medication to replace the cortisol that your glands will no longer be able to produce if they’ve been removed.
In most cases, your body will eventually recover and begin to produce the right amount of cortisol. Some patients will need to take hormone replacement drugs for the rest of their lives.
If surgery and radiation are not an option, medication can be prescribed that helps limit the production of cortisol.
If left untreated, PDCD can have serious consequences. Large amounts of released cortisol may cause diseases of the circulatory system, the network of blood vessels throughout the body.
Complications from continued large amounts of released cortisol include:
- premature atherosclerosis, an early buildup of plaque in the arteries
- impaired glucose tolerance, which can lead to problems with diabetes
- high blood pressure (hypertension)
Massachusetts General Hospital places the success rate of Cushing’s disease surgeries at between 80 and 90 percent. In most cases, the removal of the tumor in the pituitary gland will result in normal cortisol production by the adrenal glands.
Even after treatment, symptoms may take some time to dissipate as your hormone levels return to normal. Follow any lifestyle recommendations your doctor has given you during this time.