The goals of treatment are to reduce GH production to normal levels, to relieve the pressure that the growing pituitary tumor exerts on the surrounding brain areas, to preserve normal pituitary function, and to reverse or ameliorate the symptoms of acromegaly.
Currently, treatment options include surgical removal of the tumor, drug therapy, and radiation therapy of the pituitary.
Surgery is a rapid and effective treatment, of which there are two alternative methods.
The first method, a procedure known as Endonasal Transphenoidal surgery, involves the surgeon reaching the pituitary through an incision in the nasal cavity wall. The wall is reached by passing through the nostrils with microsurgical instruments.
The second method is Transsphenoidal surgery during which an incision is made into the gum beneath the upper lip. Further incisions are made to cut through the septum to reach the nasal cavity, where the pituitary is located.
Endonasal Transphenoidal surgery is a less invasive procedure with a shorter recovery time than the older method of Transphenoidal surgery, and the likelihood of removing the entire tumor is greater with reduced side-effects.
Consequently, Endonasal Transphenoidal surgery is often used as a first option, with Transphenoidal and other treatments, such as, medicinal therapy or radiostatic neurosurgery being used to reduce the remaining adverse effects of the remaining tumor.
These procedures normally relieve the pressure on the surrounding brain regions and lead to a lowering of GH levels. If the surgery is successful, facial appearance and soft tissue swelling improve within a few days.
Surgery is most successful in patients with blood GH levels below 40 ng/ml before the operation and with pituitary tumors no larger than 10 mm in diameter.
Success depends on the skill and experience of the surgeon. The success rate also depends on what level of GH is defined as a cure.
The best measure of surgical success is normalization of GH and IGF-1 levels. Ideally, GH should be less than 2 ng/ml after an oral glucose load.
A review of GH levels in 1,360 patients worldwide immediately after surgery revealed that 60 percent had random GH levels below 5 ng/ml.
Complications of surgery may include cerebrospinal fluid leaks, meningitis, or damage to the surrounding normal pituitary tissue, requiring lifelong pituitary hormone replacement.
Even when surgery is successful and hormone levels return to normal, patients must be carefully monitored for years for possible recurrence.
More commonly, hormone levels may improve, but not return completely to normal. These patients may then require additional treatment, usually with medications.
The primary current medical treatment of acromegaly is to use somatostatin analogues -- octreotide (Sandostatin) or lanreotide (Somatuline).
These somatostatin analogues are synthetic forms of a brain hormone, somatostatin, which stops GH production. The long-acting forms of these drugs must be injected every 2 to 4 weeks for effective treatment.
Most patients with acromegaly respond to this medication.
In many patients, GH levels fall within one hour and headaches improve within minutes after the injection.
Several studies have shown that octreotide and lanreotide are effective for long-term treatment. Octreotide and lanreotide have also been used successfully to treat patients with acromegaly caused by non-pituitary tumors.
Somatostatin analogues are also sometimes used to shrink large tumors before surgery.
Because octreotide inhibits gastrointestinal and pancreatic function, long-term use causes digestive problems such as loose stools, nausea, and gas in one third of patients.
In addition, approximately 25 percent of patients develop gallstones, which are usually asymptomatic. In rare cases, octreotide treatment can cause diabetes.
On the other hand, scientists have found that in some acromegaly patients who already have diabetes, octreotide can reduce the need for insulin and improve blood sugar control.
For those who are unresponsive to somatostatin analogues, or for whom they are otherwise contraindicated, it is possible to treat using one of the dopamine agonists, Bromocriptine (Parlodel) or Cabergoline.
These have the advantage of being tablets rather than injections, and cost considerably less. These drugs can also be used as an adjunct to somatostatin analogue therapy.
They are most effective in those whose pituitary tumours cosecrete prolactin. Side effects of these dopamine agonists include gastrointestinal upset, nausea, vomiting, light-headedness when standing, and nasal congestion.
These side effects can be reduced or eliminated if medication is started at a very low dose at bedtime, taken with food, and gradually increased to the full therapeutic dose.
However, bromocriptine lowers GH and IGF-1 levels and reduces tumor size in fewer than half of patients with acromegaly. Some patients report improvement in their symptoms although their GH and IGF-1 levels still are elevated.
The latest development in the medical treatment of acromegaly is the use of growth hormone receptor antagonists. The only available member of this family is pegvisomant (Somavert).
By blocking the action of the endogenous growth hormone molecules, this compound is able to control disease activity of acromegaly in virtually all patients. Pegvisomant has to be administered subcutaneously by daily injections.
Combinations of long-acting somatostatin analogues and weekly injections of pegvisomant seem to be equally effective as daily injections of pegvisomant.
Radiation therapy has been used both as a primary treatment and combined with surgery or drugs. It is usually reserved for patients who have tumor remaining after surgery.
These patients often also receive medication to lower GH levels. Radiation therapy is given in divided doses over four to six weeks.
This treatment lowers GH levels by about 50 percent over 2 to 5 years. Patients monitored for more than 5 years show significant further improvement.
Radiation therapy causes a gradual loss of production of other pituitary hormones with time.
Loss of vision and brain injury, which have been reported, are very rare complications of radiation treatments.
No single treatment is effective for all patients. Treatment should be individualized depending on patient characteristics, such as age and tumor size.
If the tumor has not yet invaded surrounding brain tissues, removal of the pituitary adenoma by an experienced neurosurgeon is usually the first choice.
After surgery, a patient must be monitored for a long time for increasing GH levels. If surgery does not normalize hormone levels or a relapse occurs, a doctor will usually begin additional drug therapy.
The current first choice is generally octreotide or lanreotide. However, bromocriptine or cabergoline are much cheaper and easier to administer.
With both types of medication, long-term therapy is necessary because their withdrawal can lead to rising GH levels and tumor re-expansion.
Radiation therapy is generally used for patients whose tumors are not completely removed by surgery; for patients who are not good candidates for surgery because of other health problems; and for patients who do not respond adequately to surgery and medication.
Further Reading
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