Acromegaly is an uncommon condition in which you make too much growth hormone. This causes various symptoms which slowly develop over several years. The most noticeable symptoms are that your hands and feet become larger, and features of your face may become more prominent. The cause is usually a small non-cancerous tumour in the pituitary gland. Treatment options include surgery to remove the tumour and medicines to block the release or effects of growth hormone.
Understanding the pituitary gland and growth hormone
The pituitary gland gland lies just below the brain. It makes several hormones, including growth hormone. (A hormone is a chemical that is made in one part of the body, passes into the bloodstream, and then can have effects on other parts of the body.)
The amount of growth hormone that you make is partly controlled by other hormones which come from a small part of the brain called the hypothalamus. This is just above the pituitary. It makes growth hormone-releasing hormone (GHRH) which stimulates the pituitary to make growth hormone when the blood level of growth hormone is low. It also makes a hormone called somatostatin which prevents the pituitary from making growth hormone when the level of growth hormone is high.
Growth hormone helps to stimulate growth and repair of various body tissues. It is needed in childhood to help children to grow. Growth hormone acts on some tissues directly. It also stimulates the liver to make another hormone called insulin-like growth factor 1 (IGF-1). Many of the effects of growth hormone are actually due to IGF-1 which acts on various cells in the body.
What is acromegaly and what causes it?
Acromegaly is a condition where you make too much growth hormone. In over 99 in 100 cases, the excess hormone comes from a small tumour in the pituitary gland. This is a benign (non-cancerous) growth called a pituitary adenoma. The adenoma may grow up to 1-2 cm across. However, as it is benign, it does not spread to other areas of the body. The abnormal cells in the adenoma make lots of growth hormone. It is not known why the adenoma develops.
Rarely, acromegaly is caused by an excess of GHRH which is made in the hypothalamus. This stimulates the cells in the pituitary to make too much growth hormone. Very rarely, other tumours in the body can make growth hormone.
Who gets acromegaly?
Acromegaly is rare. About 3 or 4 people in a million develop acromegaly each year in the UK. It mainly first develops in adults between the ages of 25-40. Men and women are equally affected.
Rarely, it affects children. If it develops in a child (usually occurs between the ages of 15 to 17), it causes the condition called gigantism because growth hormone promotes growth of bones in the body.
Note: the rest of this leaflet is about acromegaly in adults.
What are the symptoms and problems of acromegaly?
Acromegaly literally means 'enlarged extremities' or 'enlarged hands and feet'. This is a typical feature, but there are many other symptoms. The symptoms develop gradually. Some people have symptoms which develop over 10-15 years before the diagnosis is made.
It is useful to divide the symptoms into two types: those caused by too much growth hormone, and those caused by the enlarging tumour (adenoma) in the pituitary.
Symptoms caused by too much growth hormone
The excess of growth hormone in your bloodstream can affect various tissues in your body which can make them thicken or grow.
So, over time one or more of the following may develop:
- Hands and feet become larger and broader. Your glove and shoe size may increase over the years. You may not be able to get a wedding ring off.
- Your skin may thicken (particularly on the face) and become more greasy and sweaty.
- Changes to your face which may include: thickened lips and nose, thickening of your scalp, your jaw becoming more prominent. These changes develop very gradually so may not actually be noticed by your family or friends. However, looking back at old photographs may suggest your facial appearance has changed.
- Your vocal cords thicken which may cause your voice to deepen.
- Your tongue may enlarge so you may often bite your tongue.
- Thickening of cartilage may cause arthritis in various joints.
- Thickening of the nasal passages can make you snore loudly and may cause obstruction in airflow when you are asleep (sleep apnoea). This can make you have a poor night's sleep with daytime drowsiness.
- Carpal tunnel syndrome. This is where a nerve going through the wrist is squashed by thickened tissue. It can cause pain, tingling and weakness in parts of the hands or arms.
- Irregular or absent periods (in women) may occur.
Other effects of too much growth hormone may include:
- General tiredness.
- Some muscle weakness.
- About 1 in 5 people with acromegaly also develop diabetes as growth hormone counters the effects of insulin.
- High blood pressure. This develops in about 1 in 3 cases.
- Increased risk of heart disease and stroke. This is probably because of the increased risk of developing high blood pressure and diabetes.
- People with acromegaly have an increased chance of developing polyps (small benign growths) in the bowel and a slightly increased chance of developing bowel cancer. People with acromegaly are now routinely screened for these conditions (see below).
Also, in about 1 in 3 cases, the adenoma also makes too much of another hormone called prolactin. This can cause sexual and menstrual problems, and a milky discharge from the nipple. Many men with acromegaly also develop erectile dysfunction (impotence).
Symptoms caused by the growing tumour
In many cases the tumour remains small and does not cause pressure symptoms. However, in some cases the tumour grows enough to cause pressure on the nearby tissues. This can lead to:
- Problems with vision. The tumour may press on the optic nerves (the nerves going from the eyes to the brain) which are just next to the pituitary.
- Other normal cells in the pituitary may become squashed and damaged. Therefore, you may develop a lack of other hormones that are made by the pituitary. This can cause an underactive thyroid gland and/or an underactive adrenal gland which can cause various other symptoms.
How is acromegaly diagnosed?
- A blood test can measure the level of growth hormone. However, a single test is not reliable. This is because the levels of growth hormone in the body fluctuate a lot throughout the day in all people.
- The diagnosis of acromegaly is made by a glucose tolerance test. In this test you drink a sugar drink containing 75 grams of glucose. You then have a series of blood tests over two hours. The glucose should lower the blood level of growth hormone. However, if you have acromegaly, the growth hormone level remains high.
- A blood test to measure the level of IGF-1 (see above) may be measured if acromegaly is suspected. This may also be used as an index of disease activity to assess how well treatment is working.
- A magnetic resonance imaging (MRI) scan can show the size of any tumour.
- Eye and visual tests can assess if the tumour is pressing on the optic nerve.
- If you are confirmed as having acromegaly, other tests will be needed to see if the tumour is causing a lack or excess of other hormones made by the pituitary.
- Other tests may include chest X-ray, electrocardiogram (ECG) and X-rays of some of your joints.
What are the treatments for acromegaly?
The aim of treatment is to reduce the level of growth hormone in the blood to normal, and to reduce the size of an enlarged tumour. Many of the symptoms and features of acromegaly will reverse or improve with successful treatment (apart from any fixed extra bone growth that had occurred).
The most common treatment is to remove the adenoma by surgery. This is done using very fine instruments. There are two different ways to operate on the pituitary gland:
The first method is known as endonasal trans-sphenoidal surgery. This involves the surgeon reaching your pituitary gland through a small cut (incision) in wall of one of your nostrils. In the other way, the surgeon approaches the pituitary gland through a small incision behind your upper lip, just above your front teeth. The instruments are passed through the base of your skull - the sphenoid bone. The aim is to remove the adenoma, but to leave the rest of the pituitary gland intact.
The operation is successful, with no further treatment needed, in around 9 out of 10 cases with smaller tumours. The operation is less successful in those with larger tumours. However, sometimes it is not possible to remove all the cells of the tumour. If not all is removed and your growth hormone level remains high following surgery, other treatments listed below are likely to work.
Your surgeon will advise on the possible complications which can sometimes occur. For example, sometimes the operation may damage some other parts of the pituitary gland. This may cause a reduced production of some other hormones. If this occurs, you will need to take replacement hormone therapy.
Medication can be used if surgery is not possible, or not wanted. It is also used whilst waiting for surgery or radiotherapy. It can also be used in cases where surgery fails to remove the tumour totally and the level of growth hormone remains high.
- Somatostatin analogues (octreotide and lanreotide) reduce the level of growth hormone to normal in over half of cases, and reduce the size of the tumour in about 8 in 10 cases. However, these medicines need to be given as an injection. They work in a similar way to somatostatin (described above) which is a hormone that prevents growth hormone from being released from pituitary cells. These medicines used to be injected several times a day. However, longer-acting preparations are now available as monthly or fortnightly injections. Side-effects are not common with these medicines. Some people develop tummy (abdominal) pains and diarrhoea, but these usually wear off with time. Gallstones can also occur but rarely cause problems.
- Dopamine agonists (such as cabergoline, bromocriptine and quinagolide) can be taken as tablets. They work by preventing the release of growth hormone from tumour cells. However, they only work well in about 1 in 5 cases. Side-effects such as feeling sick and dizzy are also quite common.
- Pegvisomant (Somavert®) is taken as a daily injection. However, unlike the other medicines listed above, it does not act directly at the pituitary. Pegvisomant works by blocking the action of growth hormone on your body's cells. Therefore, although many of the symptoms of growth hormone excess will be eased, it does not reduce the size of the tumour and headaches are not eased.
Radiotherapy is an option to reduce the size of the tumour and hence reduce the production of growth hormone. Radiotherapy focuses high-intensity radiation at your pituitary tumour to destroy the abnormal cells. It may be used if you are not able to have surgery, or if surgery was only partially successful. However, it can take months or years after the radiotherapy is given for the level of growth hormone to reduce to normal. You can take medication whilst waiting for the effects of radiotherapy to work.
A possible side-effect of pituitary radiotherapy is damage to other normal pituitary cells. This can cause a reduced level of some other hormones. However, if this occurs you can take replacement hormone therapy.
Acromegaly and bowel cancer screening
As mentioned earlier, people with acromegaly have an increased chance of developing bowel (colonic) polyps and bowel cancer. Therefore, if you are diagnosed with acromegaly and are aged 40 or more you will normally be offered a routine colonoscopy every 3-5 years. A colonoscopy is a test where an operator (a doctor or nurse) looks into your large bowel (colon) with a flexible telescope. It can diagnose bowel problems such as polyps and bowel cancer. The aim is to detect those people who develop cancer as early as possible (before symptoms develop) when the chance of a complete cure is high.
However, you should always tell you doctor if you develop any new symptoms from your bowel such as persistent diarrhoea, passing mucus, passing blood, or tummy (abdominal) pain.
Further help & information
Dr Tim Kenny
Dr Colin Tidy
Dr Adrian Bonsall