Pituitary Tumors

Diagnosis

While making a diagnosis, the physician will ask about a family history of pituitary gland tumors, hyperparathyroidism (overactive parathyroid gland), multiple kidney stones, multiple stomach ulcers, hypoglycemia (low blood sugar), or adrenal gland tumors.

A physical exam identifies signs of pituitary tumors and other health problems. A neurological exam includes checking vision, hearing, balance, coordination and reflexes. Depending on the results, the physician may request one or more of the following tests.

Biochemical Testing

The patient's symptoms and physical exam results may lead the physician to suspect a pituitary tumor. Hormones can be measured in the blood or urine to detect excess or deficiency. Often further stimulation or suppression testing is needed.

Magnetic Resonance Imaging (MRI) Scan

MRI is the standard imaging test to identify pituitary tumors. MRI can easily identify a macroadenoma of the pituitary gland and is also good at identifying most microadenomas. But the MRI may not be able to detect many microadenomas smaller than three millimeters (about 1/8 inch). Sometimes the MRI scan finds a small abnormality in the pituitary unrelated to the patient's symptoms. Between 5 and 25 percent of healthy people have some minor abnormality of the pituitary gland that shows up on an MRI scan.

This scan uses magnetic fields and radio waves to generate images of the brain. MRI scans are particularly useful in diagnosing brain tumors because they outline soft tissues as well as bone. Sometimes a special dye is injected into the bloodstream to distinguish tumors from healthy tissue.

Venous Blood Sampling

Corticotrophin-secreting adenomas are often too small for detection by MRI scans. When patients have biochemical tests indicating excess ACTH production, but MRI results are normal, then a venous sampling study may be useful. Catheters (small tubes) are placed into the groin veins through a small nick in the skin and guided into the petrosal sinuses, two small veins on each side of the pituitary gland. After injection of corticotrophin-releasing hormone (CRH), blood samples are taken from both sides and from the arm. This test determines if an ACTH-secreting pituitary adenoma is present and can help define its location.

Biopsy

Imaging tests and blood tests can strongly suggest a tumor's characteristics. However, a biopsy (taking a sample of tumor to examine under the microscope) provides definitive verification.

Many times, physicians will not treat a tumor until a biopsy has been done. Pituitary tumors can be exceptions. Biochemical tests for some adenomas are very accurate. And some adenomas can be treated without surgery, using medicines or radiation therapy.

When removed surgically, pituitary tumors are examined under a microscope to determine the type. Studies often use special antibodies manufactured in the laboratory to identify specific pituitary hormones.