What is the pituitary gland?
The pituitary gland is a small oval-shaped gland found at the base of the brain below the optic nerve. It secretes hormones which control and regulate the other glands in the body. These glands release hormones which are responsible for the body's growth and metabolism.
The pituitary gland is divided into two parts: the anterior and posterior.
The anterior pituitary secretes six hormones:
Growth hormone - controls growth
Prolactin - stimulates production of milk after childbirth
ACTH (adrenocorticotrophic hormone) - stimulates production of hormones from the adrenal glands
TSH (thyroid stimulating hormone) - stimulates production of hormones from thyroid gland
FSH (follicle stimulating hormone) and LSH (luteinizing stimulating hormone) - stimulate activity in the ovaries of women and the testes in men.
The posterior pituitary secretes:
ADH (anti-diuretic hormone) - controls the concentration of urine
Oxytocin - stimulates the contraction of the womb during childbirth and the secretion of milk for breast feeding.
Almost all tumours of the pituitary gland are benign, that is they are non-cancerous and do not spread. They are sometimes called adenomas. Pituitary tumours are either secreting or non-secreting tumours. Secreting tumours release excess amounts of one of the pituitary hormones and are named after that hormone, e.g. prolactin secreting tumour.
Who gets pituitary tumours?
Pituitary tumours make up nearly 10% of all brain tumours. They are most commonly found in young or middle aged adults.
What causes pituitary tumours?
Like most brain tumours the cause of pituitary tumours is unknown. Research continues into finding possible causes.
Signs and symptoms
Signs and symptoms of pituitary tumours are either caused by direct pressure from the tumour itself or by a disruption in normal hormone levels. As the tumour grows it puts pressure onto the optic nerve and this often causes headaches and visual problems.
Symptoms caused by a disruption in hormone levels usually take a long time to develop. Prolactin secreting tumours are the commonest type of secreting tumour. Women with this type of tumour may notice their monthly periods stop and they may also produce small amounts of breast milk. Symptoms in men may include impotence. Infertility is common in both men and women and the tumour may be discovered during routine tests for infertility.
Symptoms of other secreting tumours will relate to the hormones which are released. Excess secretion of growth hormones can cause a condition called gigantism which leads to abnormal growth or acromegaly. (For pictures of gigantism and acromegaly, click here). This causes enlargement of the hands and feet and can also lead to high blood pressure and diabetes. A tumour which releases excess TSH causes a disruption in the body's normal metabolism. However, these tumours are extremely rare.
Over-production of ACTH can produce a number of symptoms including Cushing's syndrome which is characterised by a round or moon face, weight gain, increased facial hair in women and mental changes such as depression.
Tumours which secrete FSH or LSH are very rare and are likely to cause infertility.
Tumours in the posterior pituitary are very rare and disturbances in this area are more likely to be caused by pressure being applied to the area from the surrounding tissues. The commonest symptom of a problem in the posterior pituitary is a condition called diabetes insipidus (not the same as diabetes mellitus), the main symptom of which is passing large quantities of very weak urine.
Tests and investigations
In order for the doctors to plan your treatment they need to find out as much as possible about the type, position and size of the tumour. This is done by having a number of tests and investigations.
Pituitary tumours are often discovered during a blood test. If excess amounts of pituitary hormones are found your doctor may arrange for you to have a CAT scan or MRI scan. The scan will confirm the diagnosis of a pituitary tumour. By examining your eyes your doctor can detect pressure on the optic nerve which may indicate a tumour is present. A simple test may also be done to check your visual fields which tests your range of vision.
Surgery is the commonest treatment for most pituitary tumours. The aim of surgery is to remove the tumour and leave at least some of the normal pituitary gland behind. This is not always possible and in certain cases all the gland needs to be removed. Surgery is usually done by approaching the pituitary from the nose or by a small opening under the lip. This makes recovery after surgery much quicker than other operations for brain tumours. Your doctor will explain the operation to you in more detail beforehand.
Some prolactin secreting tumours can be treated with a drug called bromocriptine which reduces the production of prolactin. If the whole pituitary gland is removed drugs will have to be taken to replace the missing hormones.
Radiotherapy treatment, the use of high energy rays to destroy abnormal cells, is an extremely effective and safe form of treatment which is often used following pituitary surgery for all types of tumour.
Treatment of pituitary tumours is usually very successful although many people will have to continue taking hormone replacements, sometimes for the rest of their lives. Regular check ups at an endocrinology (study of hormones) clinic are likely and may continue for several years.