Causes and risk factors

In people who develop acromegaly, some of the cells in the pituitary gland which produce growth hormone, start to divide more rapidly than normal, pushing to the side and sometimes destroying the normal cells.
Continued growth of these hormone-producing cells ultimately results in the development of a benign pituitary tumour called an 'adenoma'.

These tumours are not usually cancerous and generally grow very slowly within the pituitary gland. They do not normally spread to other parts of the body.

For most people with acromegaly, the pituitary tumour produces only growth hormone. However in about one-third of people the tumour cells also produce another hormone called prolactin.

Development of benign pituitary tumour

Although the pituitary tumour is not cancerous, it is important that it is treated (either by removing it completely or reducing its size). This not only dramatically reduces the amount of growth hormone produced but can also prevent some of the problems caused by the growing tumour. As the tumour becomes larger it may press on the optic nerve and cause some loss of vision, or press on the pituitary and disrupt the gland's normal secretion of hormones, as well as cause headaches.

Why does the tumour form?

Recent research has found that in approximately one-third to one-half of patients, the pituitary tumour cells have an abnormality in a specific gene (called the gsp gene), which regulates cell growth and hormone production. Research is now ongoing to understand why this abnormality occurs and whether the formation of these tumours can be prevented.