Pituitary Tumors

Diagnosis

When 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 pancreatic gland tumors.

A physical exam identifies signs of pituitary tumors and other health problems. A neurological exam includes a check of vision, hearing, balance, coordination and reflexes.

The patient's symptoms and physical exam results may lead the physician to suspect a pituitary tumor. Depending on the results, the physician may request one or more of the following tests:

Biochemical Testing

Hormone levels can be measured in blood or urine samples through lab tests that detect excess production or deficiency. Often, further hormone stimulation or suppression testing is needed. Medications to correct hormone production levels may be prescribed by your doctor based on test results. Mayo Clinic in Minnesota offers an Endocrine Testing Center staffed by highly trained nurses who specialize in performing biochemical tests.

Magnetic Resonance Imaging (MRI) Scan

MRI, the standard imaging test for pituitary tumors, uses magnetic fields and radio waves to generate images. 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.

MRI can easily identify large tumors (macroadenomas) of the pituitary gland and is also good at identifying most small tumors (microadenomas). But MRI may not detect many microadenomas smaller than 3 millimeters (about one-eighth of an inch). Between 5 percent and 25 percent of healthy people have some minor abnormality of the pituitary gland that shows up on an MRI scan.

Petrosal Sinus Sampling

Adrenocorticotropic (ACTH) hormone-secreting pituitary tumors are often too small for detection by MRI scans. When patients have blood or urine tests indicating excess ACTH production, but MRI results are normal, petrosal sinus sampling testing may be recommended. The petrosal sinuses are two small blood vessels on each side of the pituitary gland where hormones, including ACTH, are first released.

Catheters (small tubes) are placed into the groin veins through a small opening in the skin and guided into the petrosal sinuses. After injection of corticotrophin-releasing hormone (CRH), blood samples are taken from both sides of the groin and from the arm.

This test determines if an ACTH-secreting pituitary tumor is present and also can help define its location. The presence of a tumor elevates ACTH levels and, in turn, increases cortisol hormone levels, causing Cushing's disease, a specific form of Cushing's syndrome.

Biopsy

A biopsy (taking a sample of a tumor and examining it under a microscope) may occasionally be recommended by your doctor for definitive verification. Pituitary tumors can be examined under a microscope before or after surgery to determine the tumor type.