What is Acromegaly?
Acromegaly is a disease that affects the pituitary gland, which is a tiny gland located at the base of the brain behind the nose. Acromegaly occurs when a tumour (known as an adenoma) develops in the pituitary gland and causes too much growth hormone to be produced. In most cases the tumours are benign and do not spread to other parts of the body.
The pituitary gland is responsible for controlling a number of actions and functions in the body. It controls other endocrine glands and is involved in growth and development, metabolism and reproduction. The pituitary gland creates growth hormone, also known as GH, which is involved in the body’s physical development. The amount of growth hormone produced is controlled by a section of the brain known as the hypothalamus, which produces growth hormone-releasing hormone (GHRH) to stimulate the production of growth hormone by the pituitary gland when levels of the hormone in the blood are low. The hypothalamus also produces a hormone known as somatostatin when the levels of GH in the blood are too high.
How common is Acromegaly?
Acromegaly is a rare condition with only 3-4 new cases per million people diagnosed each year in the UK. The disease can affect people of all ages but is most common in people aged between 25 and 40, affecting both men and women equally. In rare cases Acromegaly can affect children and, if an individual develops Acromegaly before they have stopped growing, this causes a condition known as gigantism.
What is the cause of Acromegaly?
Acromegaly is a result of the development of a tumour in the pituitary gland in 99 out of 100 cases. The tumour causes the gland to produce too much growth hormone, which in turn causes symptoms to develop. In very rare cases (approximately 1 percent) Acromegaly can be caused by overproduction of GHRH by the hypothalamus. In very rare cases Acromegaly can be caused by tumours in other parts of the body, including tumours in the adrenal glands, lungs and pancreas.
Symptoms of Acromegaly
The word Acromegaly literally translates as ‘enlarged extremities’, which is a symptom of the disease; however, there are many other symptoms. Symptoms tend to develop gradually and some people will wait years until their condition is diagnosed because they do not experience apparent signs. Symptoms are usually divided into two categories. These include symptoms that result from overproduction of growth hormone and others resulting from the growth of the tumour.
Symptoms of elevated levels of growth hormone include:
- Hands and feet becoming larger and wider.
- Thickening of the skin (especially on the face).
- Thickening of the facial features, including the lips and nose.
- Increased prominence of the jawbone.
- The skin becoming sweaty.
- The voice becomes deeper (this is caused by the vocal chords thickening).
- Snoring (caused by the airways becoming thicker).
- Changes to the menstrual cycle in women.
- Generally feeling unwell.
- Weakness in the muscles.
- Arthritis (caused by thickening of the cartilage in the joints).
Symptoms caused by growth of a tumour:
- Vision problems.
- Symptoms caused by changes in the levels of other hormones produced by the pituitary gland.
Complications of Acromegaly
Complications of Acromegaly include:
- Diabetes: around 1 in 5 people develop diabetes as a result of growth hormone affecting the function of insulin.
- Impotence: many men with Acromegaly experience impotence.
- High blood pressure: around one third of people with Acromegaly develop high blood pressure.
- Increased risk of bowel polyps and bowel cancer.
How is Acromegaly diagnosed?
If you experience symptoms or you feel unwell you should see your GP. They will ask about your symptoms and if they suspect that you have Acromegaly, they will refer you for further tests. Various tests can be carried out to diagnose Acromegaly, including:
- Blood tests: several blood tests will usually be carried out throughout the day, as the level of growth hormone in the blood tend to rise and fall during the day, making a single test result unreliable.
- Glucose tolerance test.
- MRI (magnetic resonance imaging): this is designed to gauge the size of the tumour.
- Eye and vision tests.
The glucose tolerance test involves drinking a glucose solution and then having a series of blood tests over a two-hour period. The glucose should lower the levels of growth hormone in the blood, but in people who have Acromegaly the levels of GH will still be high.
A blood test will also be carried to measure levels of IGF-1, a hormone which is produced by the liver. Growth hormone stimulates the production of this hormone and people with Acromegaly often experience symptoms as a result of the actions of the IGF-1 hormone. This test can also be used to show doctors how well treatment is working.
If Acromegaly is diagnosed other tests will be carried out to determine whether or not manufacture of other hormones by the pituitary gland has been affected.
Treatment for Acromegaly
The main aims of treatment are to reduce the levels of growth hormone in the blood and decrease the size of the tumour in the pituitary gland. Most symptoms can be eased effectively through treatment, though growth of bone tissue cannot be reversed.
The most common treatment for Acromegaly is surgery, which is used to remove the tumour from the pituitary gland. The procedure is carried out using delicate instruments and there are two methods used: the first is known as endonasal transsphenoidal surgery, a method which involves access to the tumour through a very tiny incision in the wall of one of the nostrils; the second method involves access to the tumour through a small incision behind the top lip. The aim of surgery is to remove the tumour without affecting the pituitary gland in any way.
In around 90 percent of cases involving small tumours surgery is successful; however, in the case of larger tumours the success rate is lower. It may not be possible for surgeons to remove all of the tumour cells, but other treatments can be used if surgery is not possible or it is not possible to remove the tumour entirely.
Medication can be used if a patient does not want to have surgery, if surgery is not possible or if growth hormone levels are still high after surgery. Types of medication used include:
- Somatostatin analogues: this medication, which is given via injections, helps to reduce the level of growth hormone in the blood. Injections used to be given throughout the day, but there are now long-term injections that last up to a month. It is not common for side-effects to be experienced with this form of medication.
- Dopamine agonists: these medicines work by preventing the tumour cells from releasing growth hormone. However, they are only successful in around one fifth of patients.
- Pegvisomant: this is a daily injection which prevents the action of growth hormone on other cells in the body.
Radiotherapy is used to reduce the size of the tumour, which subsequently decreases the production of growth hormone. It can take a long time for radiotherapy to bring growth hormones down to normal levels. Radiotherapy is usually used when surgery has been unsuccessful.
Patients who are diagnosed with Acromegaly are encouraged to have regular colonoscopy tests, as they have a slightly higher risk of developing bowel cancer. Patients are offered routine tests every three years to check for early warning signs of bowel polyps or bowel cancer.