What is acromegaly?
The pituitary gland is anatomically and functionally separated into the anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis). Table 22.1 lists the hormones found in the pituitary gland.
Acromegaly is a rare disease caused by growth hormone (GH)-secreting tumors of the pituitary. In children, GH-secreting tumors cause gigantism, whereas acromegaly occurs in adults whose epiphyses have fused. Acromegaly is most common in patients 20–60 years of age, with equal distribution between the sexes. Diagnosis generally occurs 10–15 years after the onset of pathologic growth hormone (GH) secretion. There is a twofold to fourfold increase in mortality versus the general population. If untreated, 50% of acromegalic patients die before the age of 50 years. The most common cause of death is cardiac and may be the result of hypertension, coronary artery disease, compensatory hypertrophy as a result of gen-eralized somatomegaly or the direct effects of GH on the heart.
Acromegaly results from excess secretion of GH and subsequent elevation of circulating and locally produced insulin-like growth factor I (IGF-I). GH and IGF-I levels are controlled via several interactions rather than stimulat-ing growth directly. GH induces the release of IGF-I, which promotes DNA, RNA, and protein synthesis, as well as cell and tissue growth.