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Pituitary Tumor

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What are pituitary tumors?

To understand pituitary tumors, it helps to know about the normal structure and function of the pituitary gland.

The pituitary gland

The pituitary is a small gland found inside the skull just above the nasal passages, which are above the fleshy back part of the roof of the mouth (known as the soft palate). The pituitary sits in a tiny bony space called the sella turcica. The nerves that connect the eyes to the brain, called the optic nerves, pass close by it.


The pituitary gland is connected directly to part of the brain called the hypothalamus. This provides a key link between the brain and the endocrine system, a collection of glands in the body that make hormones. Hormones are substances that are released into the blood and stimulate other organs to work. The hypothalamus releases hormones into tiny blood vessels directly connected to the pituitary gland. These cause the pituitary gland to make its own hormones. The pituitary is considered the “master control gland” because the hormones it makes control the levels of hormones made by most other endocrine glands in the body.

The pituitary gland has 2 parts, the posterior pituitary and the anterior pituitary, each of which has a distinct function.

Posterior pituitary : The smaller, back part of the pituitary gland, known as the posterior pituitary, is really an extension of brain tissue from the hypothalamus. The posterior pituitary is where the hormones made by the hypothalamus (vasopressin and oxytocin) are stored and released into the bloodstream.

Vasopressin (also called antidiuretic hormone, or ADH) causes the kidney to retain water for the body and not lose it all in the urine. Without vasopressin, a person would urinate too much and become dehydrated. This condition is called diabetes insipidus. Vasopressin also can raise blood pressure by causing blood vessels to contract and narrow. It may have other functions as well.

Oxytocin causes the uterus to contract in women during childbirth and the breasts to release milk when a woman nurses her baby. It may have other functions in both men and women as well.

Tumors rarely develop in the posterior pituitary.

Anterior pituitary : Most pituitary tumors begin in the larger, front part of the pituitary gland known as the anterior pituitary. This is not brain tissue. It is a true gland. It makes several hormones that control other endocrine glands.

Growth hormone (GH, also known as somatotropin) promotes body growth during childhood. If too much is made in a child they will grow very tall. Normally, adults make only small amounts of growth hormone. If an adult makes too much growth hormone, the bones of the hands, feet, and face continue to grow and become quite large, causing their normal features to become distorted. This condition is called acromegaly.

Thyroid-stimulating hormone (TSH, also called thyrotropin) stimulates growth of the thyroid gland and the release of thyroid hormone. Thyroid hormone regulates metabolism. Too much makes you hyperactive and shaky, and too little makes you sluggish. Overproduction of TSH by a pituitary tumor is one cause of hyperthyroidism (an overactive thyroid gland).

Adrenocorticotropic hormone (ACTH, also known as corticotropin) causes the adrenal glands to grow and to produce steroid hormones (such as cortisol). Too much of this hormone from the pituitary causes Cushing’s disease, the symptoms of which can include rapid weight gain and the buildup of fat in certain parts of the body.

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are also called gonadotropins. In women their main effects are on the ovaries, where they regulate ovulation (the release of eggs) and the production of the hormones estrogen and progesterone. In men, LH and FSH control testosterone and sperm production in the testicles.

Prolactin causes milk production in the female breast. Its function in men is not known.

Pituitary tumors : Almost all pituitary tumors are benign (non-cancerous) glandular tumors called pituitary adenomas. These tumors are considered benign because they don’t spread to other parts of the body, but they can still cause significant health problems because of their location near the brain and because many of them secrete excess hormones.

Pituitary cancers (called pituitary carcinomas) are very rare.

Pituitary adenomas : These benign tumors do not spread outside the skull. They usually remain confined to the sella turcica (the tiny space in the skull that the pituitary gland sits in). Sometimes they grow into the walls of the sella turcica and surrounding blood vessels, nerves, and coverings of the brain. They do not grow very large, but they can have a big impact on a person’s health.

There is very little room for tumors to grow in this part of the skull. Therefore, if the tumor becomes larger than about a centimeter (about half an inch) across, it can compress and cause damage to nearby parts of the brain and the nerves that arise from it.

The problems pituitary adenomas can cause include:

Vision loss or double vision: The nerves that connect the brain to the eyes (the optic nerves) and to the muscles that move the eyes pass near the pituitary gland. An enlarged pituitary can press on these nerves and affect vision.

Overproduction of hormones: Many pituitary adenomas make too much of a particular hormone, which can cause serious symptoms 

Hormone deficiency: Sometimes the pituitary adenoma can crowd out the healthy pituitary tissue that remains. Damage to this tissue can lead to a shortage of the other pituitary hormones.

Microadenoma versus macroadenoma

Pituitary adenomas can be divided into 2 categories based on size:

Microadenomas are tumors that are smaller than 1 centimeter (cm) across. Because these tumors are small, they rarely damage the rest of the pituitary or nearby tissues. But they can cause symptoms if they release too much of a certain hormone into the bloodstream. Many people may actually have small adenomas that are never detected because they never grow large enough or secrete enough hormones to cause a problem.

Macroadenomas are tumors 1 cm across or larger. Macroadenomas can affect a person’s health in 2 ways. First, they can cause symptoms if they make too much of a certain hormone. Second, they may cause symptoms by pressing on normal pituitary tissue or nearby nerves, such as the optic nerves.

Functional versus non-functional adenoma : Pituitary adenomas are also classified by whether they produce a hormone and, if they do, which type they make. If a pituitary adenoma makes hormones it is called functional. If it doesn’t make any hormones it is called non-functional.

Functional adenomas: Most of the pituitary adenomas that are found produce hormones. The hormones can be detected by blood tests or by tests of the tumor when it is removed with surgery. Based on these results, adenomas are classified as:

Prolactin-producing adenomas (prolactinomas), which account for about 4 out of 10 pituitary tumors

Growth hormone-secreting adenomas, which make up about 2 in 10 pituitary tumors

Corticotropin (ACTH)-secreting adenomas (about 7%)

Gonadotropin (LH and FSH)-secreting adenomas (less than 1%)

Thyrotropin (TSH)-secreting adenomas (less than 1%)

Some adenomas secrete more than one type of hormone.

The kind of hormone an adenoma produces strongly affects what signs and symptoms the patient has. It also affects which tests are used for diagnosis, the choice of treatment, and the patient’s outlook.

Non-functional adenomas: Pituitary adenomas that do not make any hormone are called non-functional adenomas or null cell adenomas. They account for about 3 in 10 of all pituitary tumors that are found. They are usually detected as macroadenomas, causing symptoms because of their size as they press on surrounding structures.

Pituitary carcinomas : Cancerous tumors of the pituitary gland are rare. Only a few hundred have ever been described in medical journals. They can occur at any age, but most are found in older people. These cancers usually make hormones, just like many adenomas do.

Most pituitary carcinomas look very much like pituitary adenomas under a microscope, so doctors have trouble telling them apart. In fact, there is no good way to tell if a pituitary tumor is a carcinoma and not an adenoma until the tumor spreads to another part of the body. If this happens, it is typically 5 to 10 years after the first surgery. Most often it spreads to the brain, spinal cord, meninges (the covering of the brain and spinal cord), or bone around the pituitary. Rarely, these cancers spread to other organs such as the liver, heart, or lungs.

Other pituitary tumors :There are several other types of benign pituitary tumors, as well as some malignant (cancerous) ones. All are much less common than adenomas.

Teratomas, germinomas, and choriocarcinomas are all rare tumors that usually occur in children or young adults. They do not develop from the endocrine cells of the pituitary gland itself, but they can grow into it and damage it.

Rathke cleft cysts and gangliocytomas of the pituitary are rare tumors that are usually found in adults.

Craniopharyngiomas are slow-growing tumors that start above the pituitary gland but below the brain itself. They may compress the pituitary gland and the hypothalamus, causing hormonal problems. They are more common in children, but they are sometimes seen in older adults.

Cancer that starts in sites other than the pituitary (like the breast) can metastasize (spread) to the pituitary. These cancers are classified and treated based on where they started (their primary site) and are not classified as pituitary tumors.

What are the risk factors for pituitary tumors?

A risk factor is anything that changes a person’s chance of getting a disease such as cancer. Different cancers have different risk factors. For example, smoking is a risk factor for cancer of the lung and many other cancers.

But risk factors don’t tell us everything. Having a risk factor, or even several risk factors, does not mean that you will get the disease. And many people who get the disease may not have had any known risk factors.

Pituitary tumors have very few known risk factors, and these are related to genetics. There are no known environmental or lifestyle-related risk factors for pituitary tumors.

Family history : Rarely, pituitary tumors seem to run in families. In some cases, they are found along with a number of other tumors as part of an inherited genetic syndrome (see the next section).

Sometimes, though, only pituitary tumors occur. Some of these are due to changes in a gene called AIP. These changes can be inherited from a parent but also can occur during a person’s lifetime. Most often, the cause of pituitary tumors that run in families is not known.

Genetic syndromes : Pituitary tumors can be a part of a syndrome that includes an increased risk of several types of tumors. These syndromes are caused by abnormal changes (mutations) in a person’s genes. They include:

Multiple endocrine neoplasia, type I (MEN1) is a hereditary condition in which people have a very high risk of developing tumors of 3 glands: the pituitary, parathyroid, and pancreas. It is caused by changes in the gene MEN1, and is passed on to about half of the children of an affected parent. If the MEN1 syndrome affects your family, you should discuss testing for this condition with your doctor.

Multiple endocrine neoplasia, type IV (MEN4) is a rare syndrome that includes increased risks of pituitary tumors and certain other tumors. This syndrome is caused by inherited changes in a gene called CDKN1B.

McCune-Albright syndrome is caused by changes in a gene called GNAS1 that aren’t inherited but occur before birth. People with this syndrome have brown patches on their skin (called café-au-lait spots) and develop many bone problems. They also may have hormone problems and pituitary tumors.

Carney complex is a rare syndrome in which people can have heart, skin, and adrenal problems. They also have a high risk of a number of different types of tumors, including pituitary tumors. Many cases are caused by inherited changes in the gene PRKAR1A, but some are caused by changes in other genes that have not yet been identified.

Do we know what causes pituitary tumors?

Scientists do not know exactly what causes most pituitary tumors. During the past few years, they have made great progress in understanding how certain changes in a person’s DNA can cause cells in the pituitary to produce a tumor. DNA is the chemical in each of our cells that makes up our genes – the instructions for how our cells function. We usually look like our parents because they are the source of our DNA. However, DNA affects more than how we look.

Some genes have instructions for controlling when cells grow and divide into new cells. Genes that help cells grow and divide or cause them to live longer than they should are called oncogenes. Genes that slow down cell division or cause cells to die at the right time are called tumor suppressor genes. Tumors can be caused by DNA changes that turn on oncogenes or turn off tumor suppressor genes.

Some people inherit gene mutations (changes) from their parents that greatly increase their risk for developing certain tumors. But usually, gene mutations occur during life rather than having been inherited. These acquired mutations may result from outside exposures, such as to radiation or cancer-causing chemicals, or they may just be random events that sometimes happen when a cell divides, without having an external cause. Most pituitary tumors are not cancers, and there are no known environmental causes for these tumors.

Some of the gene mutations linked to pituitary tumors that run in families were described in the previous section, “What are the risk factors for pituitary tumors?” Members of families with these genetic syndromes can have genetic testing to find out if they are affected.

Much less is known about the causes of non-hereditary (sporadic) pituitary tumors. Some of these have acquired mutations in the AIP gene. Many growth hormone-secreting adenomas have an acquired mutation in a gene calledGNAS1. These mutations are much less common in other types of pituitary adenomas.

Several other gene changes have been found in other types of pituitary adenomas, but it is not clear whether abnormal genes are always needed for pituitary tumor formation. What is known is that there is a loss of the regulatory mechanism that normally keeps the pituitary cells from growing and making too much hormone.

Because there are no known lifestyle-related or environmental causes of pituitary tumors, it is important to remember that there is nothing people with tumors could have done to prevent them.

Can pituitary tumors be prevented?

Pituitary tumors have not been linked with any known outside risk factors. As a result, there is no known way to prevent these tumors at this time. But for people at high risk of pituitary tumors, there may be ways to find and treat them early, before they cause problems

Can pituitary tumors be found early?

No imaging tests or blood tests are recommended to screen for pituitary tumors in people who are not at increased risk. (Screening is testing for tumors in people without any symptoms.)

For members of families known to be at increased risk because of a genetic syndrome such as multiple endocrine neoplasia, type I (MEN1), doctors often recommend regular blood testing of pituitary hormone levels. These tests increase the odds of finding a tumor early so that it can be removed completely, increasing the chance for a cure.

Rarely, a pituitary tumor is found early because a person has a CT or MRI scan of the brain for an unrelated problem. These tumors are sometimes referred to as incidentalomas, meaning they are found incidentally (by accident).

Functional pituitary adenomas are often found when they are still small because they produce a hormone, like prolactin or ACTH, that causes symptoms.

Non-functional pituitary tumors are less likely to be found early because they do not cause symptoms until they have grown large enough to press on normal pituitary cells, nerves, or parts of the brain near the pituitary.

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

Gonadotropin-secreting adenomas : 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.

Gonadotropin-secreting adenoma  : 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.

Thyrotropin-secreting adenoma :  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 : 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 gadoliniumis 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.

How are pituitary tumors staged?

Staging is the process of determining how far a cancer has spread. This is done to guide treatment and to help determine the most likely outcome for the patient. However, since pituitary tumors are nearly always benign, there is no staging system for them. Pituitary carcinoma is too rare for a staging system to have been developed.

Currently, the most useful information for guiding the treatment of an adenoma is:

Whether it is a microadenoma (smaller than 1 centimeter across) or macroadenoma (1 centimeter across or larger)

Whether it has grown into nearby structures (such as bones of the skull)

Whether it is functional (producing hormones) or non-functional

Which hormone it releases

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