Acromegaly

Acromegaly is often a chronic debilitating condition that, if left uncontrolled, is associated with increased morbidity and mortality.

GH stimulates hepatic production of insulin-like growth factor-I (IGF-I). GH produces some of its somatic effects directly; others are mediated by IGF-I.

Investigation:

Once acromegaly is suspected, measurement of serum IGF-I should be the next step. Acromegaly in the absence of high IGF-I levels is extremely rare.

Measuring GH during an OGTT has been a standard technique for diagnosis of acromegaly for almost 40 years. If the GH level does not decline to below 1 ng/mL during the test, the patient has acromegaly.

Although random GH levels are not generally useful in diagnosing acromegaly, patients with diabetes mellitus have
GH levels that respond to glucose; however, performance of an OGTT in patients with very high levels of glucose is not always advisable.

Low, but nonsuppressible, levels of GH after oral administration of glucose (GH >1 ng/mL) are frequently noted in patients who have undergone surgical treatment and who have normal IGF-I concentrations. In such patients, the acromegaly is considered controlled but not cured. If the patient is asymptomatic, close follow-up without therapy is reasonable. Currently, prophylactic irradiation is not considered warranted in this context. If symptoms such as heat intolerance or glucose intolerance emerge, or if the IGF-I level becomes high, further therapy is warranted.

Management:

Measurement of GHRH can be helpful in detecting an ectopic source of the acromegaly. A GHRH test should be done when a patient has no obvious pituitary tumor, but there is proven acromegaly.

• Surgical treatment should be considered the first therapeutic option in every patient with acromegaly. Those patients who present with severe mass effect manifested as visual loss or double vision are appropriate candidates for urgent surgical treatment.

• Medical therapy may be offered as first-line treatment but only after the surgical option has been discussed with the patient.

1. Somatostatin analogue such as octreotide.
2. GH receptor antagonists such as pegvisomant.
3. Dopamine agonist such as carbargoline.

• Pituitary irradiation is most commonly used as adjunctive therapy after surgical resection. In young adults who desire fertility, the patients (men and women) must be informed that any type of pituitary irradiation may impair gonadotropin function.

• Treatment of associated condition such as cardiovascular or respiratory condition. Colonoscopy should be done at the time of diagnosis of acromegaly and then follow guidelines (colonoscopy every 5 years if no cancer or polyps are detected, with more frequent follow-up if any lesions are detected ).