Growth hormone (GH) is normally produced by the pituitary gland in the brain. Excessive amounts can result if a tumor develops in the gland.
Acromegaly affects muscle strength, bone health, and energy levels, and it can lead to unusual physical features and medical complications. It can take years for the changes to appear.
Premature death is possible, and life expectancy may be reduced by 10 years.
Three to four people in every million receive a diagnosis of acromegaly in the United States (U.S.) each year, and it affects 60 people in every million at any one time.
- Acromegaly results from too much growth hormone in the body.
- It can lead to unusual physical features such as swollen hands and feet, deformities, and complications, with an impact also on muscle strength and bone health.
- The condition is most commonly caused by a tumor on the pituitary gland known as a pituitary adenoma.
- Treatment is likely to involve a combination of surgery, radiotherapy, and medication to limit growth.
Acromegaly characteristically leads to swollen hands and large feet.
The changes brought about by acromegaly take time to develop.
Changes in physical appearance can be dramatic. They include:
- a large jaw and tongue
- gaps between the teeth
- a more prominent brow
- swollen hands
- large feet
- rough and oily skin
- skin tags
Other changes include:
- tingling and lack of sensation in the hands and feet
- heavy sweating
- a deeper voice
- impaired vision
There may also be enlargement of the internal organs, including the heart, liver, lungs, and kidneys.
Acromegaly is very rare in children. It can lead to a condition called gigantism.
The overproduction of growth hormone that is associated with acromegaly normally results from a tumor.
The most common type of tumor is a non-cancerous, or benign, tumor in the pituitary gland, known as a pituitary adenoma.
The tumor causes the pituitary gland to produce excess growth hormone (GH), leading to abnormal growth.
Pituitary tumors are not genetically inherited from parents. They can appear randomly, due to a small genetic change of one cell within the gland.
Over time, this cell will replicate and form a tumor, called an adenoma. Adenomas are not malignant, because they do not spread to other parts of the body, but they may cause problems due to their size and location.
As the tumor grows, it can put pressure on surrounding brain tissue. Because the skull is a closed space, this growth can crowd the remaining tissue, leading to headaches and vision problems.
The location of the tumor means that the production of other hormones can also be affected.
The impact can be different for men and women, due to the type of hormone affected. Women may find that it affects their menstrual cycle, while some men experience impotence.
Around 17 percent of the population are thought to have small pituitary adenomas that do not usually produce excess growth hormone or cause any symptoms. It is only when a larger tumor occurs that the problems arise.
It is also important to note that most pituitary adenomas do not secrete any hormone. However, of the ones that do, growth hormone-secreting adenomas account for a third of cases.
In rare cases, a tumor elsewhere in the body, such as the lungs, adrenal glands, or pancreas, can lead to an overproduction of GH, resulting in symptoms of acromegaly.
This growth hormone may either be produced by the tumors themselves or because the pituitary gland is responding to a stimulus to produce GH. For example, some hypothalamic tumors may secrete growth hormone releasing hormone (GHRH), which tells the body to produce GH.
Sometimes, acromegaly is due to increased growth hormone production from outside the pituitary gland, such as from neuroendocrine tumors like small cell lung cancer or carcinoid tumors.
As the symptoms of acromegaly appear slowly, it can take a long time, possibly years, to make a diagnosis.
If the hands and feet swell and grow to a larger size, this can be an early sign of acromegaly. Often, people will notice it when their gloves or shoes no longer fit.
A series of tests can confirm the presence of acromegaly.
Insulin-like growth factor-1 (IGF-1): Tests can show if the level is too high. IGF-1 is a hormone that is produced in the liver. It promotes growth. People with acromegaly usually have high levels of this hormone, because high levels of GH stimulate the production of IGF-1.
Other pituitary hormones can also be measured.
Oral glucose tolerance test (OGTT): This can give a more accurate reading of GH levels.
The patient will need to fast overnight before drinking some concentrated glucose solution, and then giving a blood sample. Ingesting the glucose would normally lead to a fall in hormone levels. In a person with acromegaly, the hormone levels would remain high, because the body is producing excess GH.
MRI scan of the brain: This can determine the location and size of the tumor.
Treatment will depend on the location of the tumor, the person's age, and their medical history.
Treatment will aim to reduce excess hormone production, relieve any pressure caused by the tumor, regulate hormone levels, and improve symptoms.
Surgery may be carried out to remove the pituitary tumor. This would stop the overproduction of GH and relieve pressure on the surrounding tissue.
Transsphenoidal surgery involves inserting an endoscope through the nasal cavity to access the pituitary gland. The endoscope will pass from the nasal cavity into the sphenoid bone, which is a bone separating the brain from the rest of the facial structures.
Removing the tumor should lead to a fall in growth hormone levels. However, even if the tumor is successfully removed, hormone levels may not return to normal, and additional therapies may be necessary.
Radiation therapy can be used alone or as part of a combined approach.
After surgery, radiation therapy can remove any remaining tumor cells. It can also be used in conjunction with medication to reduce growth hormone levels.
Conventional radiation therapy is given 5 days a week, for up to 6 weeks, but it may take up to 10 years for growth hormone levels to return to normal.
In stereotactic radiosurgery, highly-focused, intense beams of radiation are directed at the tumor, minimizing damage to the surrounding tissue. This involves fewer sessions than conventional radiotherapy, and it can reduce growth hormone levels in a shorter time.
Medication to control growth
Acromegaly can be treated with medication alone if surgery is considered too risky or impossible due to the location of the tumor.
Medications include somatostatin analogs (SSAs), dopamine agonists, and growth hormone receptor antagonists (GHRAs). These aim to stop the rapid growth triggered by preventing the secretion of or the action of growth hormone.
A combination of treatments will probably be the best option.
Complications can be potentially life-threatening.
- cardiomyopathy, a type of heart disease
- carpal tunnel syndrome
- compression of the spinal cord
- hypertension, or high blood pressure
- hypopituitarism, or reduced production of other pituitary hormones
- kidney failure
- vision loss
- polyps, or precancerous growths, within the colon
- sleep apnea
- uterine fibroids
If not treated, acromegaly can have a serious effect on a person's health.