Diagnosing Pituitary Tumors

NYU Langone endocrinologists are experienced at diagnosing tumors of the pituitary, a pea-sized gland located at the base of the brain. This gland releases hormones that control a number of other glands in the body.

Functional pituitary tumors, or adenomas, produce excess levels of hormones, causing a person to develop certain hormonal conditions. They can lead to a variety of symptoms, depending on which hormones are affected. A premenopausal woman who has not given birth may produce breast milk or have irregular or absent menstrual periods, and a man might have sexual problems. People may experience increased growth of soft tissues and bones; high blood pressure; weight gain; and fat deposits on the face, upper back, shoulders, and midsection.

Nonfunctional pituitary tumors don’t cause hormone levels to rise. However, both functional and nonfunctional tumors can grow large enough to cause headaches and vision problems. Large tumors may also press on the pituitary gland and interfere with its ability to secrete hormones, causing hormone levels to drop. Symptoms can include low blood pressure, low blood sugar, fatigue, fertility problems, and decreased sex drive.

Pituitary tumors generally occur spontaneously without any known cause. However, people with a rare genetic disorder called multiple endocrine neoplasia syndromes or familial pituitary tumor syndromes may be at increased risk for functional and nonfunctional tumors. This risk may be higher in people with a history of radiation exposure.

To diagnose a pituitary tumor, an NYU Langone endocrinologist conducts a physical exam. He or she asks about any current or previous health conditions and any symptoms you may have. Then, he or she may perform one or more of the following tests.

Blood Tests

Blood tests help doctors detect many hormonal abnormalities associated with pituitary tumors. For example, a blood test can reveal high levels of the hormone prolactin, which occurs in a condition called hyperprolactinemia. This can indicate the presence of a pituitary tumor called a prolactinoma.

If a person has enlarged hands and feet, a doctor may perform a blood test to check for elevated levels of growth hormone. Some pituitary tumors produce excess growth hormone in adults, causing a condition called acromegaly. In this disorder, growth hormone signals the liver to make another hormone that “tells” the body’s tissues to grow, called insulin-like growth factor-1 (IGF-1). A blood test may reveal high levels of this hormone.

To confirm the diagnosis of acromegaly, doctors may perform a glucose tolerance test. Blood is taken before and after you drink a solution containing glucose (sugar), so doctors can measure levels of glucose and growth hormone. In people without acromegaly, a higher blood glucose level usually causes the body to stop producing growth hormone. If growth hormone levels do not drop, acromegaly may be present.

A doctor may also check for Cushing’s disease, which is caused by a pituitary tumor. With this condition, a pituitary adenoma produces too much adrenocorticotropic hormone, or ACTH, which signals the adrenal gland to make excessive amounts of cortisol, a hormone that normally helps you manage stress. Blood, saliva, and urine tests can be used to detect high levels of cortisol. Additionally, a doctor can measure blood levels of ACTH.

High levels of thyroid-stimulating hormone, or TSH, in the blood, which can cause hyperthyroidism, may, in rare cases, indicate a pituitary tumor.

Doctors may also order blood tests to check for hypopituitarism, in which there are low levels of one or more hormones released by the pituitary. This condition may occur when a tumor grows too large and interferes with normal pituitary gland function.

Vision Tests

Some pituitary tumors can press on nerves that lead from the eyes to the brain, causing vision problems. If you’re having problems with your eyesight or if your doctor suspects a pituitary tumor based on your symptoms and laboratory tests, he or she may order vision tests. Neuro-ophthalmologists—doctors who specialize in treating eye problems related to the nervous system—conduct visual field tests, which check the full scope of your vision in all directions.

MRI Scan

In an MRI, magnetic fields and radio waves are used to create computerized, three-dimensional images of the body. A doctor performs an MRI of the head to determine if a pituitary tumor is present. This scan can also help doctors determine whether a pituitary tumor is growing into nearby tissue. Before the scan, the doctor may inject a contrast agent into a vein in the arm to enhance the images.

MRI scans can help doctors determine the size of a pituitary tumor. Tumors greater than 1 centimeter are called macroadenomas and are more likely to cause symptoms such as headaches, vision problems, and a drop in hormone levels (hypopituitarism). Small tumors less than 1 centimeter in diameter are called microadenomas. These tumors are less likely to compress normal pituitary or brain tissue, but still may produce excess pituitary hormones.

Pituitary tumors that don’t cause symptoms may sometimes be discovered during imaging tests for other conditions.

Venous Blood Sampling

Very small, functional pituitary tumors that produce excessive amounts of adrenocorticotropic hormone, or ACTH, can be difficult to detect on an MRI scan. Sometimes ACTH levels may be high due to a tumor located somewhere else in the body. For these reasons, doctors may order a pituitary venous blood sampling test, also called petrosal sinus sampling.

For this test, doctors place tiny catheters—or hollow, plastic tubes—in the veins of the inner thighs or arms. They guide the catheters up to an area at the base of the brain that holds two veins that drain blood from the pituitary gland. Doctors take a blood sample from the pituitary veins and compare it to a sample taken from a vein in the arm.

If the pituitary blood sample has comparatively high levels of ACTH, it’s likely that a person has a pituitary tumor. If blood taken from a vein in the arm has a high level, then a tumor elsewhere in the body may be the problem. Sometimes a drug called corticotrophin releasing hormone, or CRH, is injected to exaggerate the difference between blood draining the pituitary and the arm blood sample.

This procedure is performed using mild sedation, and people can usually go home the same day.