Pituitary Adenoma

Tumours of the pituitary arise from the anterior portion of the gland and are nearly always benign. The pituitary gland secretes a number of different hormones that control other glands in the body. Pituitary tumours (or adenomas) are described as either “functioning” or “non-functioning”, according to whether or not they are producing excessive quantities of one or another of these hormones. Functioning tumours are named after the hormone involved. The presenting symptoms are usually the result of overproduction of a particular hormone, or possibly the result of a subsequent underproduction of other hormones. The table below shows the three most common hormones involved and their presenting symptoms:

Hormone	Hormone Function	Presenting Symptom
Growth Hormone	Controls growth	Acromegaly: The enlargement of soft tissue, and cartilage and bones in the face, hands and feet. Can produce so-called “Gigantism”.
Prolactin	Controls milk production after birth	Prolactinoma: Features may include discharge from breasts, irregular menstrual cycle, and infertility.
ACTH	Controls cortisol production by the adrenal glands. Cortisol helps the body control blood pressure, circulation, sugar levels and stress, and many other factors.	Cushing’s syndrome: Features include behavioural changes, face tends to be rounder, weight gain around the trunk (central obesity), bruising easily, muscle wasting and weakness, thinning of the skin.

Other presenting features of both functioning and non-functioning tumours include symptoms related to local pressure effects, such as visual impairment from pressure on the optics nerves, and raised pressure inside the head generally.

Treatment methods

Drug Therapy

Drugs can be used to lower abnormal levels of circulating hormones and to inhibit hormone production. This approach can cause some tumour shrinkage, particularly in the case of prolactinoma where drug treatment is usually the only method required to give excellent control of the disease.

Surgery and Radiotherapy

In most other cases management is primarily by surgery, which has a high success rate in relieving both local and hormone related symptoms. However, following surgery, there is a significant recurrence rate, and not all such tumours (especially functioning ones) can necessarily be completely removed by surgery in the first place. Post-operative radiotherapy has traditionally been used to provide further disease control, but many centres (including our own) are now beginning to report excellent results either for the use of radiosurgery as an addition to conventional radiotherapy when this latter method has also failed, or in its own right following surgery but before radiotherapy.

Gamma Knife

Gamma knife treatment is not used as primary therapy because surgery is so effective, and works more quickly to control hormone levels. Gamma Knife however, is particularly useful when treating persistent or recurrent tumours. It has been shown to be at least as effective as conventional radiotherapy in treating these recurrences, whilst reducing complications such as damage to the optic apparatus, and possibly sparing the remainder of pituitary function. Furthermore, precise calculation of the dose to vital structures such as the optic chiasm and brainstem ensures that tolerable limits are not exceeded, even where previous radiotherapy has been given as primary or secondary treatment.