A pituitary tumor is an abnormal growth of cells in the pituitary gland. The American Cancer Society estimates that nearly one out of five people in the United States will develop a pituitary tumor within his or her lifetime.
The pituitary gland is a pea-sized endocrine gland located in the center of the brain, just behind the nose and close to the optic nerves. Connected to the hypothalamus, the gland provides an important link between brain activity and the endocrine system, which is involved in producing and releasing hormones.
Doctors often refer to the pituitary gland as the “master gland” because it controls the release of hormones from other endocrine glands, such as the thyroid and adrenal glands. It regulates a number of important functions in the body such as our temperature, thyroid activity, growth during childhood, urine production, male testosterone production, and female ovulation, estrogen production, and lactation.
While most pituitary tumors do not cause symptoms, some do cause health issues. The tumor can be functional or nonfunctional, depending on whether it produces hormones. Some functional pituitary tumors produce excessive amounts of certain hormones such as growth hormone or adrenocorticotropic hormone (ACTH), which leads to the release of cortisol, a stress hormone that maintains blood pressure and glucose levels.
Types of Pituitary Tumors
With the exception of nonfunctional tumors, pituitary gland tumors are classified by the type of hormone they secrete.
These pituitary tumors make a hormone called adrenocorticotropic hormone (ACTH). When the body makes too much ACTH, it causes a disorder known as Cushing's disease.
These pituitary tumors make growth hormone, which can cause a disorder known as acromegaly in adults. In children, the condition is known as gigantism.
These pituitary tumors make prolactin, a hormone that stimulates a woman's breasts to make milk during and after pregnancy, and that can lead to loss of libido and low testosterone in men.
These pituitary tumors produce excess thyroid-stimulating hormone, causing the thyroid gland to become overactive. Tumors in the pituitary gland that secrete reproductive hormones such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH), called gonadotropin-secreting tumors, are treated similarly.
Although these pituitary tumors do not produce hormones, they can affect the secretion of reproductive hormones.
Non-Pituitary Tumors of the Sella
A part of the brain called the sella, as well as its surrounding space, can be the site of pituitary tumors as well as other types of tumors, including meningiomas, gliomas, metastatic tumors, and germinomas. In many cases our physicians can use the same surgical approaches commonly used for pituitary tumors (transnasal surgery, endoscopic surgery, intraoperative MRI) as well as radiation or chemotherapy, if needed.
Certain genetic conditions increase the chance that a pituitary tumor will develop. These conditions include multiple endocrine neoplasia (MEN) types 1 or 4, which often present with multiple tumor types; McCune Albright syndrome, which is associated with bone disorders; and Carney complex, a rare disorder that causes skin spots and tumors of the skin, nervous system, and heart.
Isolated cases of familial acromegaly (in which there is too much growth hormone) have also been reported as a risk factor for pituitary tumors.
Symptoms of a pituitary tumor vary based on the type of tumor as well as its size and location. Most people with pituitary tumors do not experience any symptoms, and are unaware that the tumor is present unless it is found by chance upon examination for an unrelated issue.
If symptoms do develop, they are often related to the disruption of the endocrine glands responsible for secreting various hormones that regulate bodily functions. Visual symptoms arise when the tumor is large enough to compress the optic chiasm (the part of the brain where the optic nerves cross), leading to loss of peripheral vision or a limiting of the visual field.