What Is Pituitary Dependent Cushing’s Disease?
Cushing’s syndrome is a condition in which the body produces far too much cortisol. 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
This over-production of cortisol can be caused by a number of factors. One form of Cushing’s syndrome is pituitary depending Cushing’s disease (PDCS). Somewhat confusingly, pituitary-dependent Cushing’s disease is often referred to simply as “Cushing’s disease.” “Cushing’s syndrome,” on the other hand, is a broader category of problems.
In PDCS, the underlying cause of the issue is a tumor in the pituitary gland. In most cases, these tumors are non-cancerous, 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, the ACTH hormone tells the body to produce more cortisol than is normally needed.
The high levels of cortisol cause symptoms including obesity and very easy bruising, among other health concerns.
Cushing’s syndrome is fairly rare. It is estimated that the condition affects about 13 in every one million people. Most cases of Cushing’s syndrome are caused by external factors—the most common cause is over-prescription or overuse of corticosteroids. However, when Cushing’s syndrome is caused by something wrong with the body, it is most commonly caused by a pituitary tumor (Adler, 2012; Kirk, et al., 2000).
Cause of Pituitary Dependent Cushing’s Syndrome
The cause of PDCS 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.
Symptoms of Pituitary Dependent Cushing’s Syndrome
The symptoms of PDCS develop due to the body’s reaction to high levels of cortisol. Because they are unable to properly metabolize fats, people with PDCS may struggle with obesity. The fat is mainly around the center of the body and is hard to get rid of.
Other common symptoms of PDCS are:
- easy bruising
- thinning of the skin
- muscle weakness
Diagnosis of Pituitary Dependent Cushing’s Syndrome
Your doctor will be able to confirm PDCS by measuring the levels of ACTH and cortisol in your body.
However, cortisol readings may differ throughout the day. To account for the differences, some tests may be performed multiple times through the day. Cortisol levels can be measured either through a blood (serum) test, or through a salivary (spit) test. In a salivary level test, cortisol levels are taken at four specific times during the day. You will be asked to provide salivary samples that are then sent out for analysis.
Your doctor may also want to use imaging techniques like magnetic resonance imaging (MRI) and computed tomography (CT) scans to get a clearer picture of the tumor. This can help determine a course of action.
Treatment of Pituitary Dependent Cushing’s Syndrome
The treatment focuses on eliminating the overproduction of ACTH by the pituitary gland. Usually, this means surgically removing the tumor (transsphenoidal pituitary adenectomy)—sometimes, however, the entire gland must be removed.
Other, less common, methods used to treat PDCS include:
- bilateral adrenalectomy (BA)—removal of one or both adrenal glands;
- gamma knife radiosurgery (GK)—tiny radiation beams focus on the tumor to destroy it and not cause harm to the tissue around it
- pituitary-directed radiation—radiation focused upon the pituitary gland
After primary treatment, your doctor will prescribe medication to replace the cortisol that your glands will no longer be able to produce. In most cases, your body will eventually recover and begin to produce the right amount of cortisol. Some patients, however, will need to take hormone replacement drugs for the rest of their lives.
Complications of Pituitary Dependent Cushing’s Syndrome
Large amounts of released cortisol may cause diseases of the circulatory system (system of blood vessels throughout the body).
Complications from continued large amounts of released cortisol include:
- premature atherosclerosis (early buildup of plaque in the arteries)
- impaired glucose tolerance (can lead to problems with diabetes)
- hypertension (high blood pressure)
Outlook for Pituitary Dependent Cushing’s Syndrome
If left untreated, PDCS can have serious consequences. The rising levels of cortisol will cause problems that can lead to obesity and heart disease.
Surgical treatment has a success rate between 69 and 90 percent (Ammini, et.al.2011). In most cases the removal of the tumor in the pituitary gland will result in normal cortisol production by the adrenal glands.