How are pituitary tumors diagnosed?
Pituitary tumors are usually found when a person goes to the doctor because of symptoms they are having. If there is a reason to suspect you might have a pituitary tumor, your doctor will use one or more tests to find out. Signs and symptoms might suggest that you could have a pituitary tumor, but tests are needed to confirm the diagnosis.
Signs and symptoms of pituitary tumors
The first symptoms caused by pituitary tumors often depend on whether they are releasing excess hormones (functional adenomas) or not releasing hormones (non-functional adenomas).
Functional adenomas may cause problems because of the hormones they release. Typically, a functional adenoma makes too much of a single pituitary hormone without making too much of the other hormones. These tumors are often detected while they are still fairly small (microadenomas). Symptoms from functional adenomas are described below, based on which pituitary hormone they secrete.
Tumors that are not making excess hormones often become large (macroadenomas) before they are noticed. Large tumors can affect nearby nerves or parts of the brain, leading to headaches and visual problems. As the tumor gets larger, it puts pressure on the normal pituitary tissue. This can lead to a loss of normal pituitary hormone production, and low levels of some normal body hormones such as cortisol, thyroid hormone, and sex hormones.
Non-functional adenomas that cause no symptoms are sometimes found because of an MRI or CT scan done for other reasons. These tumors are now being found more often as more MRI and CT scans of the brain are done. These may be the most common pituitary tumors. As long as they aren’t causing problems, they probably do not need treatment.
Large tumors (macroadenomas) and pituitary carcinomas
Pituitary macroadenomas (benign tumors larger than 1 cm) and carcinomas (cancers), whether functional or not, can be large enough to press on nearby nerves or parts of the brain, leading to neurologic symptoms that may include:
- Paralysis of eye muscles, causing double or blurred vision
- Loss of peripheral vision
- Sudden blindness
- Facial numbness or pain
- Loss of consciousness (passing out)
Vision problems occur when the tumor “pinches” the nerves that run between the eyes and the brain. Sudden loss of vision, loss of consciousness, and even death can result from sudden bleeding into the tumor.
Macroadenomas and pituitary carcinomas can also press on and destroy normal pituitary tissue, causing a shortage of one or more pituitary hormones. Depending on which hormones are affected, the symptoms might include:
- Unexplained weight loss or weight gain
- Menstrual changes or loss of menstrual periods in women
- Erectile dysfunction (trouble with erections) in men
- Decreased interest in sex, mainly in men
These tumors can also cause a shortage of the hormone vasopressin, leading to a condition called diabetes insipidus. Vasopressin, also called anti-diuretic hormone (ADH), tells the kidneys to concentrate the urine. Not having enough of this hormone causes loss of water in the urine and frequent urination. As a result, the person becomes very thirsty as the body tries to keep up with the loss of water. If severe and untreated, this problem causes dehydration and abnormal blood mineral levels, which can lead to coma and even death. Fortunately, this condition is easily treated with a drug called desmopressin, which replaces the vasopressin. Diabetes insipidus is not related to diabetes mellitus (in which people have high blood sugar levels).
Growth hormone-secreting adenomas
The major symptoms from these tumors are related to the effects of too much growth hormone. These effects are quite different in children and adults.
In children, high growth hormone levels can stimulate the growth of nearly all bones in the body. The medical term for this condition is gigantism. Its features typically include:
- Being very tall (sometimes over 7 feet)
- Very rapid growth
- Joint pain
- Increased sweating
In adults, the long bones (especially in the arms and legs) cannot grow further, even when growth hormone levels are very high. But bones of the hands, feet, and skull can grow throughout life. Adults with growth hormone-secreting adenomas do not grow taller and develop gigantism. Instead, they develop a different condition called acromegaly. The signs and symptoms of acromegaly are:
- Growth of the skull, hands, and feet, leading to increase in hat, shoe, glove, and ring size
- Deepening of the voice
- Change in the appearance of the face (due to growth of facial bones)
- Wider spacing of the teeth and protruding jaw (due to jawbone growth)
- Joint pain
- Increased sweating
- High blood sugar or even diabetes mellitus
- Kidney stones
- Heart disease
- Thickening of tongue and roof of mouth, leading to sleep disturbances such as snoring and sleep apnea (pauses in breathing)
- Thickened skin
- Increased growth of body hair
These changes can occur quite slowly, and people may not notice them until they look at an old picture of themselves (or try to put on a hat or ring they haven’t worn in many years).
Corticotropin (ACTH)-secreting adenomas
High ACTH levels stimulate the adrenal glands to produce several steroid hormones. Oversupply of these steroid hormones causes symptoms that doctors group together as Cushing’s syndrome. When the cause is high ACTH production from the pituitary it is termed Cushing’s disease. In adults, these symptoms include:
- Unexplained weight gain (mostly in the chest and abdomen)
- Purple stretch marks on the abdomen
- New or increased hair growth (on the face, chest, and/or abdomen)
- Swelling and redness of the face
- Fat areas near the base of the neck
- Moodiness or depression
- Easy bruising
- High blood sugar levels or even diabetes mellitus
- High blood pressure
- Irregular or absent menstrual periods in women
- Weakening of the bones, which can lead to osteoporosis or even fractures
Most of these symptoms can also occur in children. Children with Cushing’s disease may also stop growing and have problems with school performance.
These changes occur much faster than acromegaly, so they are more easily recognized.
Prolactin-producing adenomas (prolactinomas)
Prolactinomas are most common in young women and older men. In adult women before menopause, high prolactin levels cause menstrual periods to become less frequent or to stop. High prolactin can also cause abnormal breast milk production, called galactorrhea. In men, impotence (not being able to have an erection) or loss of interest in sex may be the first symptom.
If the tumor continues to grow, then headaches and vision problems can occur. In females who do not have periods (such as girls before puberty and older women after menopause), prolactinomas may not be noticed until they cause these symptoms.
Thyrotropin (TSH)-secreting adenomas
These rare tumors make too much thyroid-stimulating hormone (TSH), which causes the thyroid gland to make too much thyroid hormone. Patients usually have symptoms of hyperthyroidism (overactive thyroid), such as:
- Rapid heartbeat
- Tremors (shaking)
- Weight loss
- Increased appetite
- Feeling warm or hot
- Trouble falling asleep
- Frequent bowel movements
- A lump (enlarged thyroid) in the front of the neck
These uncommon tumors make luteinizing hormone (LH) and/or follicle-stimulating hormone (FSH). This may cause irregular menstrual periods in women or low testosterone levels and decreased interest in sex in men.
Many gonadotropin-secreting adenomas actually do not make enough hormones to cause symptoms, so they are basically non-functional adenomas. Before these adenomas are detected, they may become large enough to cause headaches and problems with vision.
Medical history and physical exam
If your symptoms lead your doctor to believe that you might have a pituitary tumor, the first step is take a complete medical history to check for risk factors and to learn more about your symptoms. Your doctor may ask about your family history of tumors or other problems to see if you might have an inherited genetic syndrome, such as multiple endocrine neoplasia, type I (MEN1).
Your doctor will also do a physical exam to look for possible signs of a pituitary tumor or other health problems. This may include an exam to look for nervous system problems that could be caused by a tumor.
If a pituitary tumor is strongly suspected, your doctor may refer you to an eye doctor to check your vision, as pituitary tumors can damage nerves leading to the eyes. The most common test is to measure how well you can see. The doctor may also test your field of vision (or visual fields). At first, pituitary tumors only press on part of the optic nerves. This leads to parts of a person’s vision being lost. This is usually the peripheral vision, meaning things that you can see off to the side without actually looking directly at them. Eye doctors have special instruments that can test for this.
Blood and urine tests of hormone levels
Your symptoms and physical exam results may lead your doctor to believe that you might have a pituitary tumor. If your doctor suspects you have a hormone-producing tumor, hormone levels in your blood and/or urine will be measured.
Growth hormone-secreting adenoma
A physical exam may alert the doctor to look for this tumor because the signs and symptoms are often very distinctive (see above).
The next step is to check for excess growth hormone production. Levels of growth hormone and insulin-like growth factor-1 (IGF-1) will be measured in your blood samples, which are taken the morning after an overnight fast. When growth hormone levels are high, they cause the liver to make more IGF-1. Testing the IGF-1 level can be more helpful than checking the level of growth hormone, because the IGF-1 level doesn’t change much during the day, while the level of growth hormone can go up and down.
If both levels are very high, the diagnosis is clearly a pituitary tumor. If the levels are slightly increased, another test called a glucose suppression test is often done to be sure. You will be asked to drink a sugary liquid, and the levels of growth hormone and blood sugar will be measured at intervals afterward. The normal response to suddenly taking in so much sugar is a drop in growth hormone levels. If the growth hormone levels remain high, a pituitary adenoma is probably the cause.
Corticotropin (ACTH)-secreting adenoma
Most of the signs and symptoms of ACTH-secreting tumors come from having too much cortisol (an adrenal steroid hormone). Quite a few diseases can cause the body to make too much cortisol. Patients with symptoms suggesting this condition need tests to determine if a pituitary tumor is the cause.
These tests may include measuring levels of cortisol and ACTH in blood samples taken at different times of the day. The patient may be asked to collect all the urine that they produce over a 24-hour period, which is then tested to measure daily production of cortisol and other steroid hormones. Blood or urine cortisol levels may be checked again after taking a dose of a powerful, cortisone-like drug called dexamethasone. Levels of cortisol in the saliva late at night can also be checked. These tests help to distinguish patients with ACTH-secreting pituitary tumors from patients with other diseases, such as adrenal gland tumors, that may cause similar symptoms.
Prolactin-secreting adenoma (prolactinoma)
Blood prolactin levels can be measured to check for a prolactinoma.
Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels can be checked to see if a patient has a gonadotropin-secreting tumor. Levels of related hormones, such as estrogen, progesterone, and testosterone, are often checked as well.
Tests to measure blood levels of thyrotropin (TSH) and thyroid hormones can usually identify people with a thyrotropin-secreting adenoma.
Non-functional (null cell) adenoma
A pituitary adenoma is considered non-functional if it does not make too much of a pituitary hormone. Pituitary hormone levels are not high in people with non-functional tumors. Sometimes, though, blood levels of some pituitary hormones may actually be low because the adenoma crowds out the cells that normally make these hormones.
Testing for diabetes insipidus
Diabetes insipidus is caused by damage to the part of the pituitary that stores the hormone vasopressin (ADH). This condition can be caused by pituitary macroadenomas and carcinomas in rare cases, or by tumors starting in parts of the brain or nerves next to the pituitary gland. It can also be a side effect of surgery to treat pituitary tumors or tumors next to the pituitary gland.
In many cases, this diagnosis is made with tests that measure sodium levels in the blood and osmolality (total salt concentration) of the blood and urine. If these tests are inconclusive, then a water deprivation study may be done. In this test, you are not allowed to drink fluids for several hours. The test is often done overnight. If your body is not making enough vasopressin, you will continue to make urine even though you are not taking in any fluid. You may also be given an injection of vasopressin to see if this corrects the problem.
Venous blood sampling
Corticotropin-secreting adenomas may be too small to be seen on imaging tests such as MRI scans (see the next section). When the ACTH level is high, but a person’s MRI scan is normal, a venous sampling test may be useful to find the tumor.
For this test, catheters (small tubes) are placed into veins on each inner thigh through small nicks in the skin and are guided all the way up into the petrosal sinuses near the base of the brain. The sinuses hold 2 small veins that drain the blood from each side of the pituitary gland. After an injection of corticotropin-releasing hormone (CRH, a hormone from the hypothalamus that normally causes the pituitary to secrete ACTH), blood samples are taken from both sides and compared to see if the ACTH level is higher on one side than the other. If it is, the source of the high ACTH level is a pituitary tumor.
Imaging tests use x-rays, magnetic fields, or other means to create pictures of the inside of your body. They may be done to look for pituitary tumors or to see if they have grown into nearby structures. In some cases, an imaging test of the head done for another reason may detect a pituitary tumor.
Magnetic resonance imaging (MRI) scan
MRI scans use radio waves and strong magnets to create detailed pictures of the inside of the body. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern into a very detailed image of parts of the body. A contrast material called gadolinium is sometimes injected into a vein to improve the quality of the image.
MRI scans are very helpful in looking at the brain and spinal cord and are considered to be the best way to identify pituitary tumors of all types. The images they provide are usually more detailed than those from CT scans (see below). MRI can show macroadenomas of the pituitary gland, as well as most microadenomas. But MRI may not be able to detect microadenomas that are smaller than 3 mm (about 1/8 inch) across. Sometimes the MRI scan will show a small abnormality in the pituitary that has nothing to do with the patient’s symptoms. Between 5% and 25% of healthy people have some minor abnormality of the pituitary gland that shows up on an MRI scan.
MRI scans can take a long time – often up to an hour. You have to lie inside a narrow tube, sometimes with a small frame around your head, which can be confining and may upset people with a fear of enclosed spaces. Newer, open MRI machines may help with this, but they may provide less detailed images and can’t be used in all cases. The machine also makes buzzing and clicking noises that may be disturbing. Some people may need medicine to help them relax for the test.
Computed tomography (CT) scan
The CT scan is an x-ray test that creates detailed cross-sectional images of part of your body. Instead of taking one picture, like a standard x-ray, a CT scanner takes many pictures as the camera rotates around you while you lie on a table. A computer then combines these pictures into an image of a slice of your body. Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body.
A CT scanner has been described as a large donut, with a narrow table in the middle opening. You will need to lie still on the table while the scan is being done. CT scans take longer than regular x-rays, and you might feel a bit confined by the ring while the pictures are being taken.
Before the test, you may get an injection of a contrast dye through an IV (intravenous) line. This helps better outline any tumors that are present. The injection can cause some flushing (redness and warm feeling). A few people are allergic to the dye and get hives or, rarely, have more serious reactions like trouble breathing and low blood pressure. Be sure to tell the doctor if you have any allergies or have ever had a reaction to any contrast material used for x-rays.
CT scans can find a pituitary adenoma if it is large enough, but MRI scans are used much more often to look at the brain and pituitary gland.
Tests of pituitary tissue samples
In diagnosing tumors of most parts of the body, imaging tests and blood tests may strongly suggest a particular type of tumor, but a biopsy (taking a sample of the tumor to examine under the microscope) is usually the only way to be certain of that diagnosis. In many situations, doctors will not treat the tumor until a biopsy has been done.
A pituitary tumor is an exception to this general rule in that a biopsy is not usually needed before treatment. One reason is that the hormone tests for some types of adenomas are very accurate, so a biopsy isn’t likely to provide much more information. Biopsies in this part of the body can also pose a very small risk of serious side effects. On top of this, some types of adenomas can be treated without surgery, using medicines or radiation therapy.
When pituitary tumors are removed by surgery, they are examined under a microscope to determine their exact type. Special stains may be used to color the areas making hormones, which helps classify the tumor.
Last Medical Review: 01/11/2013
Last Revised: 01/11/2013