The pituitary gland is an important gland in the brain, and is often referred to as the "master endocrine gland" because it secretes a variety of hormones that affect many bodily functions. Examples of hormones secreted by the pituitary gland include:
- Thyroid stimulating hormone, which stimulates the activity of the thyroid gland
- Adrenocorticotropic hormone (ACTH), which is released in response to stress and, in turn, controls secretions of other glands
- Gonadotropins, which act on the testes or ovaries to stimulate production of sperm or eggs
- Growth hormone, which promotes growth of the long bones in the limbs
- Prolactin, which stimulates milk production after childbirth
- Lipotropin, which stimulates the transfer of fat from the body to the bloodstream
Pituitary glands have two lobes, anterior and posterior, and each is responsible for releasing specific hormones. Therefore, tumors in these glands can be very serious, as a malfunctioning pituitary gland can cause serious symptoms in other organs or systems. Generally, pituitary tumors are benign (noncancerous) growths and are classified as pituitary adenomas.
A risk factor is anything that increases a person's chance of developing a disease, including cancer. There are risk factors that can be controlled, such as smoking, and risk factors that cannot be controlled, such as age and family history. Although risk factors can influence disease, for many risk factors it is not known whether or not they actually cause the disease directly. Some people with several risk factors never develop the disease, while others with no known risk factors do. Knowing your risk factors and communicating with your doctor can help guide you in making wise lifestyle and health-care choices.
There are no known risk factors for pituitary gland tumors. However, a familial syndrome called multiple endocrine neoplasia type I (MEN1) can cause an increased risk of pituitary tumors in affected family members. Another familial syndrome, known as Carney complex, can also raise the risk of a pituitary gland tumor.
People with a pituitary gland tumor may experience the following symptoms. Sometimes, people with these tumors do not show any of these symptoms. Or, these symptoms may be similar to symptoms of other medical conditions. If you are concerned about a symptom on this list, please talk to your doctor.
- Vision problems
- Changes in menstrual cycles in women
- Impotence (the inability to achieve or maintain an erection) in men caused by hormone changes
- Infertility (the inability to have children)
- Inappropriate production of breast milk
- Cushing's syndrome, caused by overproduction of ACTH
- Acromegaly (enlargement of the extremities or limbs) from overproduction of growth hormone
Doctors use many tests to diagnose cancer and determine if it has metastasized (spread to distant locations in the body) or if it is invading structures around its site of origin. Some tests may also determine which treatments may be the most effective. For most types of tumors, a biopsy is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized or is locally invasive. Very few pituitary tumors ever metastasize, and when they do they are called "pituitary carcinoma" instead of the much more common, benign "pituitary adenoma." Your doctor may consider these factors when choosing a diagnostic test:
- Age and medical condition
- The type of cancer
- Severity of symptoms
- Previous test results
The following tests may be used to diagnose a pituitary gland tumor:
Neurological examination. An evaluation of the patient's central nervous system may include testing of the reflexes, motor and sensory skills, balance and coordination, and mental status.
Laboratory tests. A blood test is available that measures the amounts of certain hormones. A 24-hour urine sample, which requires the collection of all urine during that time frame for laboratory testing, may be necessary. This allows the doctor to track the production rate of various hormones.
Computed tomography (CT or CAT) scan. A CT scan takes x-rays of the head from many different angles. A computer then puts these images into a detailed, cross-sectional view that shows any abnormalities or tumors.
Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. MRI is better than a CT scan in diagnosing most pituitary tumors.
Lumbar puncture (spinal tap). A needle is inserted into the lower back until it enters the space that contains the spinal fluid. The spinal fluid drips out into collection tubes and is tested for substances that are distinctive for certain tumors.
Biopsy. A biopsy removes a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a diagnosis for certain.
The treatment of a pituitary gland tumor depends on the size and location of the tumor, whether it is cancerous, whether it has spread, and the person's overall health. In many cases, a team of doctors will work with the patient to determine the best treatment plan.
It is also important to state that some people with pituitary tumors need no treatment. Pituitary tumors are sometimes diagnosed in people where the tumor is not creating any symptoms and in whom hormone functions are completely intact. These patients need to undergo occasional surveillance (also called watchful waiting) to ensure that the tumor does not become more active.
The goal of surgery is to remove as much of the tumor as possible without harming nearby structures. Surgery for a pituitary tumor is often successful, but requires a surgeon skilled in this form of surgery. About 95% of surgeries to remove pituitary tumors are done by the transsphenoidal route (through the sphenoid sinus), with the remainder done through a craniotomy (an opening in the skull).
Radiation therapy is the use of high-energy x-rays or other particles to kill cancer cells. The most common type of radiation treatment is called external-beam radiation, which is radiation given from a machine outside the body. When radiation treatment is given using implants, it is called internal radiation therapy. In selected cases, stereotactic forms of radiation therapy (delivering a high dose of radiation directly to the tumor) are applied to residual pituitary tumor left after a partial surgical removal. Not all patients with residual tumor require radiation therapy, because some benign pituitary tumors do not grow back even when some is left behind after surgery.
Side effects from radiation therapy include tiredness, mild skin reactions, and upset stomach. Most side effects go away soon after treatment is finished. However, when the pituitary gland is included in the field of radiation, its ability to produce hormones can be impaired gradually over several years after the conclusion of the treatment.
Hormone replacement therapy (HRT)
HRT is often necessary for the treatment of a pituitary tumor, and may include replacement of thyroid and adrenal hormones. The drug bromocriptine (Parlodel) is used to treat tumors that secrete prolactin, and octreotide (Sandostatin) or pegvisomant (Somavert) can be used to treat those that secrete growth hormone or thyroid stimulating hormone.
The medications used to treat cancer are continually being evaluated. Talking with your doctor is often the best way to learn about the medications you've been prescribed, their purpose, and their potential side effects or interactions with other medications.
Side Effects of Cancer and Cancer Treatment
Tumors and tumor treatment can cause a variety of side effects; some are easily controlled and others require specialized care. Below are some of the side effects that are more common to a pituitary tumor and its treatments.
A pituitary tumor causes symptoms by any of three mechanisms:
By producing too much of one or more hormones
Growth hormone: causes acromegaly, a syndrome that includes excessive growth of soft tissues and bones, high blood sugar, high blood pressure, heart disease, and pain symptoms (including headache)
Thyroid stimulating hormone: causes high production of thyroid hormone, leading to nervousness and irritability, fast heart rate and high blood pressure, heart disease, excess sweating and thin skin, and weight loss.
Prolactin: causes inappropriate secretion of breast milk (even in men), osteoporosis, loss of sex drive, infertility, irregular menstrual cycles, and impotence.
Adrenocorticotropic hormone: causes weight gain (particularly in the trunk, not the legs or arms), high blood pressure, high blood sugar, brittle bones, emotional changes, stretch marks on the skin, easy bruising.
Gonadotropins (FSH and LH): usually not elevated enough to produce direct symptoms, but in extreme cases can cause infertility and irregular menstrual cycles.
By compressing the pituitary gland and thus making it produce too little of one or more hormones
Growth hormone: causes poor muscle strength, irritability, weakening of bone strength, and overall feeling of malaise (feeling unwell).
Thyroid stimulating hormone: causes fatigue and low energy, and weight gain.
Prolactin: causes inability to breastfeed after a woman gives birth to a baby.
Adrenocorticotropic hormone: causes fatigue and low energy, low blood pressure, low blood sugar, and upset stomach.
Gonadotropins (FSH and LH): cause infertility and irregular menstrual cycles.
By compressing the optic nerves or (less commonly) the nerves controlling eye movements, and thus causing either loss of part or all of the visual field, or double vision.
Treatment of a pituitary tumor can cause:
Diarrhea or gastrointestinal upset. In people being treated for excess growth hormone, the treatment can cause gallstones, therefore people receiving this treatment must be screened for them throughout the treatment period.
Fatigue (tiredness). Fatigue is extreme exhaustion or tiredness.
After treatment for a pituitary gland tumor ends, talk with your doctor about developing a follow-up care plan. This plan may include regular physical examinations and/or medical tests to monitor your recovery for the coming months and years. Follow-up care for a pituitary gland tumor may include tests to measure hormone levels and MRI scans to learn how the tumor responded to treatment. Tell your doctor about any new symptoms.
During treatment, patients with pituitary tumors may experience a number of symptoms that may affect the ability to function fully and conduct a normal life; however after treatment, most people can lead full and active lives. Those with impaired vision are among those that may need special accommodation after treatment. Studies show that those most affected following treatment are those with Cushing's disease. Some people with excess prolactin (a hormone that stimulates lactation and the secretion of progesterone) or excess growth hormone may also be significantly affected.
Once surgery to remove a pituitary tumor has been performed, the patient is typically followed by both an endocrinologist and a neurosurgeon. Yearly MRI scans are performed for five years, and possibly longer in some instances. Hormone testing is often carried out on an annual basis.
Radiation therapy can have late effects, in particular the decreasing hormone production from the pituitary gland. These can take five to seven years to develop, but it does not occur in all patients.
As most pituitary tumors are non-cancerous, second malignancies are not typically an issue. Those patients with excess growth hormone are at higher risk of developing colon cancer, but only if the tumor was not completely removed and growth hormone levels are persistently high. People with MEN-1 syndrome needs surveillance for the other tumors (of the parathyroid gland and pancreas) associated with that condition, but most people treated for a pituitary tumor simply need surveillance to ensure that the tumor is not recurring.