Neurosurgery

Non-Functioning Pituitary Adenoma

What do I have?

A large percentage of patients with pituitary tumors have a tumor that does not produce any hormone. These tumors carry a number of different names that can be confusing (“non-functioning”, “endocrine-inactive”, “null-cell”), but they all mean the same thing; the tumor is not a factory for excess production of one particular hormone, but instead is an abnormal, benign tissue growth that causes problems by taking up space where it is not welcome.

What does it do?

Because these tumors do not produce an excess of one particular hormone, and do not cause symptoms that can be detected early, most non-functioning pituitary adenomas are discovered only when they cause symptoms from “mass effect”, a medical term meaning that the growing tumor causes pressure on things that do not like being pressed. The normal pituitary gland is the first thing to feel the effects of a growing non-functioning pituitary adenoma. When the normal pituitary gland is sufficiently compressed by the tumor, it is unable to regulate normal hormone function, leading to a slow but progressive decline in hormone production. In men, the first effects are decreased libido and erectile dysfunction caused by decreased testosterone in the blood; if the tumor causes more compression, thyroid hormone levels will drop, leading to hypothyroidism (fatigue, constipation, muscle pain, depression, cold intolerance, weight gain). In women, the effects can be more complex depending on whether the patient is pre- or post-menopausal. In pre-menopausal women, non-functioning pituitary adenomas can cause menstrual periods to become irregular or stop completely, and can cause infertility. In post-menopausal women, the effects can be more subtle because the woman is no longer menstruating regularly; in these patients, the symptoms are typically related to decreased sexual interest, or the effects of hypothyroidism as discussed before. The most dangerous consequence of pituitary dysfunction is the loss of cortisol, which can be life-threatening, with symptoms such as low blood pressure, confusion, nausea, vomiting and fever.

If a non-functioning pituitary adenoma continues to grow, it will eventually enlarge to the point where it is not only pressing on the normal pituitary gland, but also pressing on other nerves and arteries at the base of the brain that are near the pituitary gland. Usually the optic nerves that connect the eyes to the brain are the next “victim” of tumor compression; this can lead to blurring of the vision or loss of peripheral vision. Extremely large pituitary tumors can even cause pressure on the brain, leading to seizures or blockage of the normal flow of cerebrospinal fluid (a condition called hydrocephalus, or “water on the brain”).

In addition to causing pressure on the normal pituitary gland and adjacent nerves and brain, a non-functioning pituitary adenoma can cause pressure on the lining around the brain and the pituitary gland, leading to increasing headache usually behind the eyes.

It is always important to keep in mind that even large pituitary adenomas are not cancer, but if left untreated, it can cause serious illness because of its effects on the normal pituitary gland, optic nerves, and brain.

How long have I had it?

Often the changes associated with these tumors are subtle, and they are typically slow growing, so it is likely that the tumor has been there for years before it was discovered. In addition, some patients have no symptoms at all from their tumor; in these cases, an MRI or CT scan was performed to help diagnose and treat an unrelated problem, and the tumor was discovered “incidentally”.

Can it be cured?

If your tumor is causing symptoms or changes in hormone balances, then the majority of these tumors can be cured or controlled through a combination of surgery and radiation therapy. The first line of treatment is surgery, unless the patient has other medical conditions that make surgery unsafe. If surgery is not possible, or if the whole tumor cannot be removed, then radiation therapy (often radiosurgery) is an option as well.

Some non-functioning pituitary tumors may be observed without treatment because they are not causing any symptoms or changes in hormone function, and because these tumors typically grow very slowly. This is often the recommended form of treatment for older patients (however, there is no specific age limit for pituitary surgery) or who have a serious medical illness such as heart disease. If a decision is made to observe the tumor without treatment, you may need continued hormone testing, and you may need periodic visual testing with an ophthalmologist, all of which will be coordinated by the Multidisciplinary Neuroendocrine clinic. CT or MRI scans are performed three to six months after initial diagnosis and every six to 12 months thereafter until the situation has been clarified. This period of observation without treatment provides information which helps the doctors decide if it is necessary to use other treatments or to recommend surgery.

At this time, there are no medical options for treating non-functioning pituitary adenomas, except for hormonal replacement to treat the hormonal imbalances caused by the tumor pressing on the normal pituitary gland.

What caused it?

For the majority of pituitary tumors, there is no known cause. These tumors appear to develop in a surprising number of patients without any clear reason. Recent work has suggested that there may be certain changes in the DNA of these tumors that lead to their formation, but their true cause remains elusive and is an active area of research.

In rare cases, these tumors may be part of a syndrome that can be inherited in families. For that reason, if anyone else in your family has ever had kidney stones, or has ever had a pituitary tumor, or has had any tumor of other hormone-producing organs (like the thyroid gland, the parathyroid gland, the kidneys, the adrenal glands, the pancreas, or the reproductive organs), let us know so that we can determine if your family is potentially a carrier for this inheritance.


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