Diagnosis of pituitary gland tumours

Diagnosis is the process of finding out the cause of a health problem. Diagnosing a pituitary gland tumour usually begins with a visit to your family doctor. Your doctor will ask you about any symptoms you have and may do a physical exam. Based on this information, your doctor may refer you to a specialist or order tests to check for a pituitary gland tumour or other health problems.

The process of diagnosis may seem long and frustrating. It’s normal to worry, but try to remember that other health conditions can cause similar symptoms as pituitary gland tumours. It’s important for the healthcare team to rule out other reasons for a health problem before making a diagnosis of a pituitary gland tumour.

The following tests are usually used to rule out or diagnose pituitary gland tumours. Many of these same tests may be used to find out if the tumour has grown into nearby organs. Your doctor may also order other tests to check your general health and to help plan your treatment.

Your health history is a record of your symptoms, risk factors and all the medical events and problems you have had in the past. Your doctor will ask questions about your history of:

• symptoms that suggest a pituitary gland tumour
• certain hereditary conditions, such as multiple endocrine neoplasia type 1 (MEN1) and familial isolated pituitary adenoma (FIPA)

Your doctor may also ask about a family history of:

• pituitary gland tumours
• risk factors for pituitary gland tumours
• other endocrine tumours

A physical exam allows your doctor to look for any signs of a pituitary gland tumour. During a physical exam, your doctor may:

• check your eyes and vision
• check reflexes
• measure your blood pressure

Find out more about physical exams.

An eye exam is done by a doctor to check your vision and the health of your eyes. It is often done by a doctor that specializes in the eyes (called an optometrist).

An eye exam checks:

• how well you can see, including your side (peripheral) vision
• eye movements
• for abnormal areas on the surface of the eyes and inside the eyes

A pituitary gland tumour can press on the nerve that connects the brain to the back of the eye (optic nerve). An eye exam lets the doctor look for any pressure on or damage to the optic nerve, which can mean there is a tumour.

A neurological exam is a series of questions and tests to check brain, spinal cord and nerve function. A neurological exam involves checking:

• mental status
• balance and coordination
• ability to walk normally
• how well the muscles, senses and reflexes work

Blood chemistry tests measure certain substances in the blood, such as hormones. They show how well certain organs are working and can help find abnormalities.

Doctors will measure certain hormone levels in the blood if there are signs or symptoms of a pituitary gland tumour. Functioning pituitary gland tumours make too many hormones and cause higher than normal hormone levels in the blood. Even if a pituitary gland tumour is non-functioning and doesn’t make too many hormones, it can press on parts of the pituitary gland or damage the gland. This can cause lower levels of hormones than normal. Blood chemistry tests may be used to check the levels of hormones such as:

• prolactin
• follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
• estrogen and progesterone
• testosterone
• growth hormone and insulin-like growth factor-1 (IGF-1)
• adrenocorticotropic hormone (ACTH)
• steroid hormones, such as cortisol
• thyroid-stimulating hormone (TSH), thyroxine (T4) and triiodothyronine (T3)

Find out more about blood chemistry tests.

An oral glucose tolerance test may be done to more accurately measure growth hormone levels in the blood. It is also called a growth hormone suppression test. Normally a higher blood sugar (glucose) level causes the body to stop making growth hormone. With the oral glucose tolerance test, a doctor can raise your blood sugar level to check how your growth hormone level responds. If the growth hormone level in the blood stays high during the test, it usually means you have acromegaly or gigantism (too much growth hormone causing increased growth of the skull, bones of the face, jaw, hands and feet). Acromegaly or gigantism is usually caused by a pituitary gland tumour.

You will be asked to not eat or drink anything for about 10 to 12 hours before the test (this is called fasting). A blood sample is usually taken in the morning while you are still fasting. Then you drink a very sweet sugar drink. Blood samples are often taken every 30 minutes for 2 hours. The levels of sugar and growth hormone in your blood are measured in each blood sample.

A dexamethasone suppression test gives a drug (called dexamethasone) to check if the body is making too much cortisol (called Cushing syndrome). The level of cortisol is usually measured in the blood, but it can also be measured in the urine.

You take a dose of dexamethasone by mouth (orally). A blood sample is taken 12 hours later to measure the level of cortisol.

Dexamethasone is a corticosteroid drug that is similar to the natural cortisol in the body. Normally the level of cortisol should decrease after taking dexamethasone. If the cortisol level in the blood doesn’t decrease after taking the dexamethasone, it may mean that there is an ACTH-producing pituitary gland tumour.

A 24-hour urine test measures certain substances in urine collected over a 24-hour period. It may be done to check the levels of cortisol and other steroid hormones in the urine. High cortisol levels may mean that there is an ACTH-producing pituitary gland tumour.

A 24-hour urine test may also be done to measure the amount and concentration of urine to check for diabetes insipidus (too much water being lost in the urine).

Magnetic resonance imaging (MRI) uses powerful magnetic forces and radiofrequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3-D pictures. A contrast medium called gadolinium is often used to help areas show up better.

An MRI is used to look for pituitary gland tumours or to find out if a pituitary gland tumour has grown into nearby areas. It may also be used to measure the size of a tumour.

An MRI is commonly used to look at the brain, spinal cord and pituitary gland. Doctors think that MRI is the best way to find pituitary gland tumours.

Find out more about MRIs.

A computed tomography (CT) scan uses special x-ray equipment to make 3-D and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures.

A CT scan may be used to look for pituitary gland tumours when an MRI can’t be done.

Find out more about CT scans.

Some tumours may be too small to be seen with imaging tests such as an MRI. When someone has high levels of ACTH but a normal MRI scan, doctors may order a venous blood sampling test to help diagnose a tumour.

For venous blood sampling, catheters are placed into veins in both inner thighs and guided by x-rays into the sinuses near the base of the brain (petrosal sinuses). These sinuses contain 2 small veins that drain blood from the pituitary gland. Blood samples are taken from both veins and compared. A higher than normal level of ACTH on one side may mean there is a pituitary gland tumour.

During a biopsy, the doctor removes tissues or cells from the body so they can be tested in a lab. A report from the pathologist will show whether or not cancer cells are found in the sample.

For most pituitary gland tumours, a biopsy isn’t done because blood chemistry tests and imaging tests are very accurate at making a diagnosis. Also, some pituitary gland tumours can be treated without surgery.

If a pituitary gland tumour is removed by surgery, a pathologist looks at it under a microscope to find out the exact type. Special stains are used to find the areas of the tumour making too many hormones and help classify the tumour.

Find out more about biopsies.

To make the decisions that are right for you, ask your healthcare team questions about a diagnosis.