Nonfunctioning Pituitary Adenoma

Family Nurse Practitioner and clinical trials patient care coordinator, Chris Yedinak, examines a patient

About nonfunctioning pituitary adenomas

Pituitary adenomas are noncancerous or benign tumors that affect the pituitary gland. About 40 percent of all pituitary adenomas are nonfunctioning, meaning they do not produce any hormones or cause extra hormones to be produced. Whether these tumors create a health issue depends on the size of the adenoma.

Of the people who have pituitary adenomas, about 10 percent have tiny tumors called microadenomas. These tumors are 2–3 millimeters in diameter, about the size of a peppercorn. Most people with microadenomas don’t know they have them, and these tumors rarely cause symptoms. Doctors are not usually concerned about these very small tumors. However, if a microadenoma grows, it can cause compression of surrounding structures.

A macroadenoma is a pituitary adenoma larger than 1 cm, about the size of a pencil eraser. As a macroadenoma grows, it can cause headaches, vision problems and other symptoms.

The exact cause of nonfunctioning pituitary adenomas is unknown. They are usually benign and slow growing. Scientists believe they may be the result of a mutation in a pituitary gland cell.

A pituitary adenoma can cause:

  • Pituitary hormone deficiencies
    As the pituitary adenoma grows, it can damage normal pituitary tissue. This can cause the pituitary gland to make fewer hormones than normal. The pituitary gland might be damaged permanently. If this happens, you might need to take extra hormones in a pill form, even after the adenoma is removed with surgery.
  • Headaches
    The pain comes from the tumor stretching the covering (meninges) of the brain. Removing the tumor usually relieves the headaches. Pituitary tumors can also cause sudden, intense headaches when part of the tumor dies. A sudden, intense headache, often described as “the worst headache of my life,” can be the presenting sign of pituitary apoplexy (the dying of the center of a large tumor due to it outgrowing its blood supply).
  • Vision loss
    Pituitary tumors often press on the area where nerve fibers carry information from your peripheral (side) vision. If the tumor is not treated, you could become blind, but vision problems usually go away if the tumor is removed.
  • Cranial nerve disturbances
    If the pituitary tumor presses on the cranial nerve, you may have problems aiming your eyes in the right direction.

Your doctor will give you a full physical examination and discuss your symptoms and medical history. Tests usually include:

  • Blood tests
    We may draw several vials of blood to perform one or more specialized blood tests that can help determine if your pituitary is producing too much prolactin, GH or ACTH hormone, or to detect other associated pituitary hormonal abnormalities. We will also give women of childbearing age a pregnancy test.
  • Cosyntropin/ACTH stimulation tests 
    A vital function of your pituitary gland is to stimulate the production of cortisol from your adrenal glands. This normally happens on a 24-hour cycle, with higher levels being produced in stressful situations when more energy is needed. We will draw blood for an initial or baseline measure of both ACTH and cortisol levels. Then, we give you a small dose of a synthetic form of ACTH through an IV in your arm. We will draw another blood sample to measure cortisol levels 30 minutes later. If there is an adequate rise in the cortisol level, there is no need for further testing. In some circumstances, a second test may be needed with a higher dose of ACTH if the first test is inconclusive.
  • MRI
    Your referring provider may have previously ordered an MRI to determine the presence of a pituitary tumor. MRIs can determine the size and location of any mass in your pituitary and show if a pituitary tumor may be affecting your eyesight.
  • Other tests
    After our providers have reviewed the data, we may recommend more specific testing. This may include a vision evaluation by a neuro-ophthalmologist.

If you have a macroadenoma, removing the tumor is the most effective option. At the OHSU Pituitary Center, our experienced neurosurgeons (doctors specializing in the nervous system) can usually remove it using a minimally invasive method through the nose. If it is a very large tumor, your neurosurgeon may use a different technique. If your neurosurgeon is not able to remove the entire tumor, you may have radiation treatment to shrink tumor tissue or to keep the tumor from growing.

If your neurosurgeon can fully remove the tumor, then recurrence is rare, but does happen in about 20–30 percent of cases overall. The success rate improves for smaller tumors and decreases for larger ones. Removing the tumor can greatly improve vision and headaches for most people. Some people also regain pituitary function that had been impacted.

After surgery, you will continue to check in with your doctor regularly, have hormonal testing and have an MRI each year for at least five years.

Clinical trials are the last step in a lengthy process of research. These studies allow scientists to test the value of their research to diagnose, treat and prevent diseases and disabilities. Each clinical trial is an opportunity to test a promising invention or treatment.

The OHSU Pituitary Center is a national leader in research related to pituitary conditions.

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