Alternative names for non-functioning pituitary tumours
Non-functioning pituitary adenomas; Non-secretory pituitary adenomas/tumours; Non-secretory pituitary adenomas/tumors; Null-cell pituitary adenomas/tumours; Null-cell pituitary adenomas/tumors; Chromophobe pituitary adenomas/tumours; Chromophobe pituitary adenomas/tumors.
Non-functioning pituitary tumours are benign tumours of the pituitary gland. They are formed from pituitary cells that do not themselves produce any active pituitary hormones and are therefore called ‘non-functioning’.
What causes non-functioning pituitary tumours?
No specific causes for non-functioning pituitary tumours are known. Normal multiplication of cells in the pituitary gland requires a specific sequence of events. If this sequence is disrupted, abnormal cell multiplication can result in the growth of these tumours. It is believed some of these disruptions may be caused by the presence and action of specific genes, some of which have been identified.
What are the signs and symptoms of non-functioning pituitary tumours?
People with non-functioning pituitary tumours develop symptoms very slowly as these tumours do not produce any hormones. As a result, these tumours also tend to be quite large by the time they are identified. They commonly cause headaches as well as more specific symptoms related to pressure on nearby critical brain structures or the optic nerves.
Pressure on the normal pituitary gland can result in hypopituitarism or pituitary failure. Production of one, some or all the pituitary hormones may fail and symptoms develop depending on which hormones have been affected and decreased. Pressure on the pituitary gland can also sometimes cause overproduction of the hormone prolactin and cause symptoms similar to another benign pituitary tumour called a prolactinoma. Pressure on the nerves to the eyes, which run near to the pituitary gland, can cause loss of peripheral vision. People are unable to see to the sides of their visual fields and sometimes complain of bumping into things that they were unable to see. If these tumours grow sideways, they can put pressure on the nerves that control the movements of the eyes and cause double vision.
How common are non-functioning pituitary tumours?
Non-functioning pituitary tumours are the most frequent big pituitary tumours measuring over 1cm in size (macroadenomas). In the UK, non-functioning pituitary tumours are the second most common type of pituitary tumour and it is estimated that as many as 22 in every 100,000 adults may have this type of tumour at any one time. Non-functioning pituitary tumours are the most common pituitary tumours in individuals over the age of 60 years and the most common in men.
Are non-functioning pituitary tumours inherited?
Non-functioning pituitary tumours can occur as an inherited condition, but this is rare. Multiple endocrine neoplasia type 1 syndrome is a genetic condition that runs in families. People with this condition can develop tumours in various endocrine glands including non-functioning tumours of the pituitary gland.
How are non-functioning pituitary tumours diagnosed?
When a non-functioning pituitary tumour is suspected, a number of different outpatient tests are carried out. Detailed magnetic resonance imaging (MRI) scans, or in some cases computerised tomography (CT) scans are required to confirm the presence of a tumour. These scans also provide information about the direction and extent of spread of the tumour and show any visible contact of the tumour with the surrounding brain structures that may suggest possible pressure-related damage.
Blood tests are required to check the level of the hormones, which are either produced by the pituitary gland or controlled by the pituitary gland. These blood tests may be one-off samples or may require more detailed testing in a day unit. These tests measure levels before and after the hormones are stimulated to see if the normal pituitary gland is working adequately. Tests usually last between one to four hours.
As these tumours can cause pressure effects on the nerves to the eyes, ‘visual field’ testing may be done. This is a test that people may be familiar with from a routine eye check by an optician. Individual dots of light appear and disappear one after the other in different areas of a special computerised light screen. As the lights come on, people confirm that they are able to see them.
How are non-functioning pituitary tumours treated?
Non-functioning pituitary tumours require an operation to surgically remove the tumour. There are currently no effective and proven medical treatments which can shrink non-functioning pituitary tumours. The operation is usually performed by reaching the tumour via the nose using a very thin high powered telescope and very fine instruments. The procedure usually lasts two to four hours under a general anaesthetic. Most people will leave hospital within two to three days.
If the tumour is too large for this method, it may have to be removed by a slightly bigger surgical procedure called a craniotomy which involves opening up the scalp and one of the skull bones. During the operation, surgeons try to save the normal pituitary tissue but this is difficult and not always possible. Surgeons also try to remove as much of the tumour as possible but this again is not always possible as the tumour may have spread to areas that are inaccessible and dangerous. This may be close to blood vessels or nerves that might be damaged by trying to operate too close to them. If total removal is not possible, people may go on to have radiotherapy or X-ray treatment to treat the remaining tumour.
Are there any side-effects to the treatment?
The most common risk of surgery, as well as that of radiotherapy, is damage to the normal pituitary tissue (if this has not already occurred as a result of pressure on the normal pituitary gland by the tumour itself). This may result in pituitary failure and deficiency of one, some or all pituitary hormones. The deficient hormones will require long-term or lifelong replacement, which is possible through hormone replacement therapy. The blood vessels that supply the brain are close by and any damage to them during surgery can very occasionally cause strokes.
Post-operative bleeding can cause pressure and damage to the eye nerves causing loss of vision. This is more commonly temporary, but can be permanent. Sometimes there can be a persistent leak of the fluid surrounding the brain from the nose (people often mistake this for a simple runny nose). In rare cases, this can lead to meningitis and may need a surgical procedure to plug the leak. In the hands of an experienced surgeon, these complications are all very rare.
What are the longer-term implications of non-functioning pituitary tumours?
Initially, patients will need to have regular follow-up appointments to ensure that their pituitary gland is functioning correctly and they may need to have follow-up MRI scans to check that treatment has been successful. People with pituitary failure may need to take multiple long-term or lifelong hormone replacement therapy. People who have been treated for a non-functioning pituitary tumour often report that they fatigue more quickly than they used to. The effects of pituitary failure or hypopituitarism may therefore require certain changes to lifestyle. Some people report that their memory is not as good as it was before they developed a non-functioning pituitary tumour, although this varies from person to person and is not always the case. Managing fatigue usually helps with memory difficulties as a tired person is less able to remember things than someone feeling well rested.
Reviewed: December 2014