40% of all cancers spread to the brain
Pituitary tumours form in or on the pituitary gland. They are not officially classified as brain tumours, but fall within the category of endocrine (hormone) system tumours: which means that these patients get extra care. Part of the multi-disciplinary team looking after somebody with this type of tumour would therefore include a neuro-endocrinologist who specialises in supporting the balance of hormones, as well as the same people who would care for someone with a brain tumour.
What is a pituitary gland?
The pituitary gland is a small structure, about the size of a pea, attached to the base of the brain behind the nose. It lies in a small hollow in the skull, just below the eye, where it is protected by a part of the skull called the sphenoid bone.
Just above the pituitary gland lies the hypothalamus, which produces hormones that control when the pituitary produces and releases hormones of its own. Together they orchestrate the delicate balance of hormones made by glands throughout the body including thyroid, ovaries and testes. The pituitary gland directly produces hormones that control the function of certain organs such as the breasts, uterus and kidneys. The pituitary therefore influences many processes including growth, development, and reproduction.
The majority of tumours that arise within the pituitary gland are classified as pituitary adenomas. Pituitary adenomas are benign, slow-growing tumours. Most pituitary adenomas are microadenomas which are small tumours less than 1cm in diameter, although a few patients have macroadenomas, which are larger.
Some types of adenomas release extra hormones into the bloodstream, hence causing symptoms. However not all adenomas produce hormones: about one third of those diagnosed are classified as non-functioning or null cell adenomas, and these cause symptoms because they grow and place pressure on the pituitary gland and surrounding brain tissue.
Is a pituitary adenoma benign or cancerous?
Pituitary adenomas are generally considered to be benign, although some are more aggressive than others. They do not spread to other parts of the brain, but remain within the pituitary gland.
How common are pituitary adenomas?
- Pituitary adenomas are the third most common tumours found within the skull in adults, making up about 10% of the total number.
- They are discovered in approximately 77 out of 100,000 people
- It is possible that they actually occur in as many as 20% of people at some point in their lives, but cause no symptoms or are so small that they are never found.
- Pituitary adenomas can occur at any age, but are more common in people in their 30s or 40s and rare in those under 20 years old.
- Women get adenomas more often than men.
What are the symptoms of a pituitary tumour?
Because the pituitary gland has such varied functions, a tumour can be difficult to diagnose because the symptoms will differ between patients. The symptoms are often due to changes in the levels of the hormones that the gland produces, and there is a range of reasons why those hormone levels may fluctuate and cause symptoms, hence delaying the diagnosis of a tumour.
Symptoms caused by hormonal fluctuations include:
- Delayed puberty in children
- Changes in menstrual periods or early menopause in women
- Increased or decreased sexual drive
- Extreme growth spurts in both children and adults, particularly of either hands or feet
- Unexplained weight gain or loss, sometimes combined with a loss of appetite
- Extreme tiredness and/or listlessness
- Personality changes such as hostility, depression, anxiety
- Low blood pressure
- Loss of muscle mass in adults
- Easy bruising of the skin, often combined with muscle weakness
- Changes in the sense of smell
- Vision problems such as blurring, double vision, loss of peripheral vision
- Nausea and vomiting
- Cushing’s disease, caused by too much adrenocorticotropic hormone (ACTH) being released, which triggers the adrenal glands to make too much of the stress hormone, cortisol
- Hyperthyroidism, caused by too much thyroid stimulating hormone (TSH) being released, giving rise to symptoms such as rapid heartbeat and an increased metabolic rate
If the tumour is large enough to press upon surrounding brain tissue, the symptoms may be very similar to those of other brain tumours found in this part of the brain.
Read more about symptoms of a brain tumour here.
How is a pituitary tumour diagnosed?
The most reliable way to diagnose any kind of brain tumour is initially by an MRI scan and then by taking a biopsy (a small sample of the tumour, removed during neurosurgery) for analysis in a laboratory. The presence of a pituitary tumour can also be indicated by tests that measure the levels of specific hormones within the blood.
What causes a pituitary tumour?
Research is underway to understand more about the genetic mutations that influence the development of this tumour type. Most seem to arrive with no clear cause, although there are a few cases of pituitary tumours appearing within a family group.
There are certain hereditary conditions which give an increased risk of pituitary tumours, the most common one being multiple endocrine neoplasia, type 1 (MEN 1), for which there is a genetic test to establish if this is the case. MEN I causes multiple tumours to arise in various glands of the endocrine system, not just the pituitary gland.
Treatment options for pituitary tumours
The treatment options for pituitary adenomas include surgery, drugs and a form of radiotherapy called stereotactic radiotherapy.
Neurosurgery for pituitary adenomas
Endoscopic transsphenoidal pituitary adenoma resection is carried out under general anaesthetic. An endoscope (a tiny light and camera on a long tube) is inserted into the nostril towards the base of the tumour. Surgical instruments are then inserted next to the endoscope through the same nostril. The tumour is removed and the bony floor of the space occupied by the pituitary is closed.
Patients usually undergo this procedure via the right nostril, however surgery is sometimes done via the left nostril, depending on the location of the tumour.
Stereotactic radiotherapy for pituitary adenomas
Stereotactic radiotherapy (SRT) is sometimes used for small brain tumours, usually those that are only 3-4cm across and in an easily accessible part of the brain, relatively close to the skull. It consists of very precisely focused gamma ray or x-ray beams at higher doses than are used in standard radiotherapy.
The advantage of this treatment is that is can be more closely targeted at a brain tumour than standard radiotherapy and surrounding healthy tissue can be spared, hence reducing the side effects of the treatment.
Chemotherapy for pituitary adenomas
Certain types of pituitary adenoma exhibit more aggressive behaviour than others, and these would be treated with chemotherapy drugs. However because this is so unusual, there is no standard chemotherapy treatment. The choice of drugs is therefore guided by the genetic profile of the tumour in each individual case, although temozolomide (Temodar) is likely to be considered.
Side effects of treatment for pituitary tumours
One of the potential side effects of tumour removal is that the pituitary gland is no longer able to make hormones. People may then be required to take hormone supplements to bring these back to normal levels, and would need to remain on these supplements for the rest of their lives.
How can we find a cure for pituitary brain tumours in the UK?
Research we are funding across all of our dedicated Research Centres will help lead towards finding a cure for a wide range of brain tumours.
Our team at the University of Plymouth Low-Grade Brain Tumour Research Centre are researching a number of molecular pathways that influence immune system function, tumour metabolism and tumour growth in a range of low-grade brain tumours in children and adults.
Scientists at our Research Centre in the University of Portsmouth are looking at repurposing drugs for a number of different types of brain tumours. They are also studying mitochondria, exploring ways to ‘shut down’ these ‘batteries’ that supply energy to the brain tumours.
The team of research and clinical experts in our Research Centre at Imperial College, London, are studying the way in which the ketogenic diet works in brain cancer, which may have the potential to influence a wide range of brain tumours.
Pioneering research at our Brain Tumour Research Centre at Queen Mary University of London is focused on using GBM stem cells to help develop unique, patient-specific treatments. Their findings are expected to translate into other types of adult and paediatric brain tumours.
We also fund BRAIN UK at Southampton University, the country’s only national tissue bank registry providing crucial access to brain tumour samples for researchers from all clinical neuroscience centres in the UK, effectively covering about 90% of the UK population, and an essential component in the fight to find a cure for pituitary brain tumours.