What Causes Pituitary Tumours To Occur?
As yet there is no research that has identified a cause of pituitary adenomas. There are some very rare inherited conditions that lead to hormone producing tumours in multiple locations in the body (M.E.N syndrome I and II), this can affect the pituitary gland
Craniopharyngiomas and rathke’s cleft cysts are not tumours in the conventional sense, but are more akin to cells that are in the wrong place and continue to divide and grow. As an embryo your pituitary gland is formed from the roof of your mouth as a pocket that becomes pinched off, this pocket eventually becomes the anterior lobe of the pituitary gland. It is thought that craniopharyngiomas and rathke’s cleft cysts form from cells forming the lining of the mouth that get accidently dragged along and pinched off together with the pituitary cells
Virtually all pituitary tumours are benign, very very occasionally a tumour arising in the pituitary can become malignant, or a tumour from elsewhere in the body spreads to the pituitary gland. Overall 99% of pituitary tumours are benign.
What Are The Differing Types of Pituitary Tumours?
Doctors classify pituitary tumours based on the cell type that they are composed of.
A simple way of classifying these tumours is:
- Those tumours that produce excess hormones ( e.g. Cushing’s disease, acromegaly, prolactinoma)
- Those tumours that produce no hormones ( non-functioning adenoma)
- Tumours arising from ‘rests’ of cells left during development ( craniopharyngioma and Rathke’s cleft cyst)
- Tumours arising from nearby structures ( meningiomas)
- Inflammatory conditions of the pituitary, pituitary stalk and hypothalamus ( hypophysitis, sarcoidosis, histiocytosis)
- Malignant tumours that have spread to the pituitary gland (lung cancer, breast cancer etc)
- Non-tumours e.g an aneurysm of the carotid artery in the pituitary fossa
How Do Pituitary Tumours Lead To Problems?
The two main ways in which these tumours cause problems is either a disturbace in hormone levels in the body ( either overproduction or underproduction of a hormone) or compression of structures near the pituitary gland ( disturbance of vision due to compression of the optic nerves)
As MRI scans are performed more and more we are seeing many patients in whom a pituitary tumour has been discovered, these may or may not be related to the symptoms being investigated, and don’t always need treatment. Other associated symptoms include headache, double vision, facial pain, and rarely impairment of memory and concentration
For further information on specific pituitary tumours please select an option on the right
What Investigations Will You Require?
Tests of how the pituitary gland is working
These comprise blood tests for the most part. The hormone levels in the blood tend to vary with the time of day and whether you are stressed or not. Many of these tests involve a series of blood tests following an injection or sugar drink, and thus you may need to come into hospital just for the day. Sometimes ( especially in Cushing’s disease) more complicated tests are required and you may need an overnight stay in hospital
The aim of these tests is to determine whether the pituitary gland is able to produce the hormones required for healthy living, respond to the stresses of daily life, and to see if hormones are being produced in excess quantities
If an operation is planned, as part of your preoperative assessment you will have your hormone levels assessed during a day in hospital at the Oxford Centre for Diabetes, Endocrinology and Metabolism under the care of Professor Wass and Dr Helen Turner
A brain scan of the pituitary gland
In almost all cases this will take the form of an MRI scan, details on MRI scans are available via the menu on the right under patient info
Occasionally we might repeat your MRI scan, this is especially true if you have a microadenoma and the tumour is so small as to be not visible on your scan. Under these circumstances a high resolution scan after an injection of dye may be performed which can identify tumours not visible on conventional scans, this technique is called dynamic imaging of the pituitary
The above scans have been performed in a patient with acromegaly due to a pituitary microadenoma. On the left the tumour is not visible, on the right contrast has been given and scans taken at 30 second intervals, the scan at 60 seconds revealed the small tumour labelled
Formal assessment of vision
Every patient with a pituitary tumour will need a formal assessment of their vision. This will involve a test of your ability to read small letters on a chart, and a test of your field of vision using a special piece of equipment
Many patients with tumours producing hormones may be at risk of developing additional problems due to the long-term effects of high levels of growth hormone or cortisol/ACTH. In acromegaly this can lead to hypertension, diabetes, impairment of breathing due to a narrow airway, respiratory disease and a higher rate of bowel cancer. Thus investigations to document these potential problems may be needed prior to surgery. The same is true of Cushing’s disease where checks for additional adrenal tumours and the effects of diabetes and hypertension may be needed.