Diagnosis of pituitary gland cancer

Diagnosis is the process of finding out the cause of a health problem. Diagnosing cancer often means first ruling out other health conditions that share similar symptoms with cancer. It can be a very worrying time for you and your loved ones. Sometimes this process is quick. Sometimes it can feel long and frustrating. But it’s important for doctors to get all the information they need before making a diagnosis of cancer.

Almost all pituitary gland cancers are pituitary neuroendocrine tumours (PitNETs). Diagnosing a PitNET 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 will refer you to a specialist or order tests to check for pituitary gland cancer or other health problems.

The following tests are usually used to rule out or diagnose pituitary gland cancer. Many of the tests that are used to diagnose cancer are also used to find out how far the cancer has spread. 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 pituitary gland cancer
• 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 cancer
• risks for pituitary gland cancer
• other endocrine cancers

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

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

Find out more about physical exams.

An eye exam is done by an eye specialist (called an optometrist). It is used to check:

• your vision and the overall health of your eyes
• how well you can see, including what you can see in front of you (central vision) and to the side (peripheral vision)
• eye movements
• for abnormal areas on the surface of and inside the eyes

A PitNET can press on the nerve that connects the brain to the back of the eye (called the optic nerve). An eye exam can show if there is any pressure on or damage to the optic nerve that may be caused by a tumour.

A neurological exam is a series of questions and tests used to see how well the brain, spinal cord and nerves are working. A neurological exam checks:

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

Blood chemistry tests measure certain substances in the blood. They show how well certain organs are working and can help find problems.

Doctors will measure certain hormone levels in the blood if there are signs or symptoms of pituitary gland cancer. Functioning pituitary neuroendocrine tumours make too much of a certain hormone and cause higher than normal levels of this hormone in the blood. Non-functioning tumours don’t make any hormones, but they can press on parts of the pituitary gland and cause lower than normal hormone levels.

Depending on your signs and symptoms, you may have blood chemistry tests to check the levels of different hormones, including:

• 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.

A growth hormone suppression test may be done to measure growth hormone levels in the blood. It’s also called an oral glucose tolerance test.

When the level of blood sugar (glucose) is higher than normal, the body will stop releasing growth hormone. During a growth hormone suppression test, your blood sugar level is raised to check how your growth hormone level responds.

• In adults, high growth hormone levels during the test can be caused by acromegaly. This is when too much growth hormone causes the bones in the skull, jaw, hands and feet to grow.
• In children, too much growth hormone can cause increased growth of the arms and legs (called gigantism).

Acromegaly and gigantism are almost always caused by a PitNET.

Before the test, you'll be asked not to eat or drink anything except water for about 10 to 12 hours. The healthcare team will take a blood sample, and then you'll have a very sweet drink made with sugar. More blood samples are taken every 30 or 60 minutes for 1 to 2 hours. The levels of sugar and growth hormone in your blood are measured in each blood sample.

If the growth hormone level in the blood stays high during the test, you may be diagnosed with acromegaly or your child may be diagnosed with gigantism. Your doctor will order other tests to check if pituitary gland cancer or another type of tumour is causing the increase in growth hormone.

A dexamethasone suppression test may be done to measure the cortisol level in the blood. Dexamethasone is a type of corticosteroid. It slows down the production of cortisol. You'll be given dexamethasone as a pill that you swallow. In 12 hours, the healthcare team will collect a blood sample.

• If there is no PitNET, the level of cortisol in your blood will be lower than normal.
• If there is a PitNET, the level of cortisol will be normal or high.

A 24-hour urine test measures the level of hormones in the urine over a 24-hour period. It may be done to check the levels of cortisol and other steroid hormones. If a PitNET is making adrenocorticotropic hormone (ACTH), the level of cortisol in the urine will be higher than normal.

A 24-hour urine test may also be done to measure the amount and concentration of urine. This is done to check for arginine vasopressin deficiency, which is when a low level of the hormone vasopressin causes the body to make too much 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 3D pictures. A contrast medium called gadolinium is used to make areas with cancer show up more clearly.

An MRI is used to look for a PitNET or to find out if cancer has grown into nearby tissue. It may also be used to measure the size of a tumour.

Find out more about MRIs.

A computed tomography (CT) scan uses special x-ray equipment to make 3D 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 is sometimes used to look for pituitary gland cancer.

Find out more about CT scans.

Sometimes a PitNET is too small to show up on an imaging test such as an MRI. If someone has high levels of adrenocorticotropic hormone (ACTH) but the healthcare team doesn’t see anything with an imaging test, doctors may order a venous blood sampling test to diagnose pituitary gland cancer.

A flexible tube called a catheter is placed into a vein in each thigh. The doctor uses an x-ray to guide the catheters through the body and into the base of the brain. Blood is taken from the veins that drain from the pituitary gland.

If a blood sample taken from one vein has a higher level of ACTH when compared to the rest of the body, there may be a PitNET.

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