What are pituitary cysts?

Pituitary cysts are fluid-filled sacs that develop on or near the pituitary gland.

The pituitary gland is a pea-sized organ located in the center of the brain, between and behind the eyes. It produces and regulates the release of hormones that control growth, sexual development and function, metabolism and the body’s response to stress.

Pituitary cysts are not cancerous, which means they do not spread to other parts of the brain or other parts of the body. Many are small and cause no health problems. Pituitary cysts that grow large enough to put pressure on the pituitary gland or on nearby nerves or brain tissue can be a health concern.

Types of pituitary cysts

Several types of pituitary cysts have been identified, including:

• Rathke cleft cysts. These are a commonly diagnosed form of pituitary cysts. They typically form as a result of an error during development of the fetus before birth, at the point where the two sections of the pituitary gland (the anterior and posterior pituitaries) join, also referred to as the Rathke’s pouch. When this pouch fails to merge into the pituitary and close during fetal development, it can leave a gap between the two sections, called a Rathke’s cleft. Occasionally, a remnant of the developing Rathke’s pouch becomes a cyst within that gap, known as a Rathke cleft cyst. They can grow large enough to cause health problems. At larger sizes, they are also more likely to be detected on brain imaging scans than very small cysts.
• Pars intermedia cysts. Like Rathke cleft cysts, these develop at the point where the anterior and posterior pituitaries join. In some other animals, this is where a third section of the pituitary forms: the pars intermedia. Pars intermedia cysts are usually small, and cause no symptoms or health problems. But a small cyst detected in this area can’t easily be distinguished from a Rathke cleft cyst in an early stage of growth.
• Arachnoid cysts. These develop when the arachnoid membrane, the middle of the three membranes surrounding the brain and spinal cord, develops a fluid-filled fold that extends into the area of the pituitary gland.
• Epidermoid cysts. These cysts are formed from bits of skin or other tissue that become misplaced during early development of the embryo and fetus. These usually occur as lumps under the skin on other parts of the body, but in rare cases can form near the pituitary gland.
• Craniopharyngioma. Sometimes, cysts form within a craniopharyngioma which sometimes need to be removed or drained.

Some pituitary tumors can have fluid-filled portions. These fluid-filled tumors can sometimes look like cysts in brain imaging, and the doctor diagnosing the condition must distinguish between them. Pituitary tumors are not covered in this description.

Causes of pituitary cysts

Most pituitary cysts form as a result of an error during development of the fetus before birth. The cause of this malformation is not known.

Signs and symptoms

Small pituitary cysts often produce no symptoms and cause no health problems.

In rare cases, larger pituitary cysts in a child or adolescent can put pressure on the pituitary gland and nearby brain tissue and nerves, including the optic nerves. It is this pressure that causes symptoms to occur. The pressure of these cysts can sometimes result in reduced production of one or several pituitary hormones. Occasionally, the pressure of the cyst on the pituitary gland causes the pituitary gland to overproduce a certain pituitary hormone. With pressure on the optic nerves, visual changes can sometimes arise.

• When an enlarged cyst puts  enough pressure on the pituitary gland, hormone production can decrease, causing symptoms that can include abnormal slowdown of growth
• Delayed puberty
• Extreme thirst and frequent urination
• Less frequent menstrual periods
• Low blood sugar (hypoglycemia)
• Sensitivity to cold
• Weight loss or weight gain
• Unusually dry skin
• Nausea or dizziness

Fatigue or drowsiness When an enlarged cyst forces enough pressure on certain areas of the pituitary gland, it can sometimes cause an overproduction of a certain pituitary gland hormone called prolactin, which causes:

• Discharge from the breasts, not related to pregnancy or nursing

Lastly, if an enlarged cyst places pressure on the optic nerve area, other symptoms that can arise include:

• Some loss of vision (narrowing field of vision, for example)
• Frequent headaches

These symptoms may resemble other conditions or medical problems. Always consult your doctor for a diagnosis.

Testing and diagnosis of pituitary cysts

Your doctor will usually begin with a physical exam and questions regarding any symptoms you may have noticed.

• Height and weight will be charted to look for changes in growth patterns.
• The doctor will check to make sure there are no abnormalities in pubertal development.

If signs indicate the possibility of pituitary cysts, additional tests may include:

• Neurological exam to check mental status, coordination, reflexes and muscle function
• Eye test to check for loss of vision, including narrowing field of vision
• Blood, urine and saliva tests to check hormone levels; the blood tests, or venous sampling, involve taking blood from peripheral veins in the arms to look at hormone levels originating from the pituitary gland in the brain
• Magnetic resonance imaging (MRI) or computerized tomography (CT) scan to get visual images of the pituitary gland, brain and spinal cord

Because symptoms of a pituitary cyst rarely arise throughout childhood, a cyst may be diagnosed when brain imaging is done for another reason.