Acromegaly

DEFINITION

• A clinical syndrome resulting from excessive secretion of growth hormone (GH).
• GH excess prior to closure of the epiphyseal plates results in gigantism; after epiphyseal plate closure, the result is acromegaly.
• Somatic and metabolic effects of chronic GH hypersecretion are predominantly mediated by high levels of insulin-like growth factor-1 (IGF-1).
• Acromegaly is an uncommon secondary cause of diabetes.
• Excess GH: 1) stimulates gluconeogenesis and lipolysis, causing hyperglycemia and elevated free fatty acid levels; 2) leads to both hepatic and peripheral insulin resistance, with compensatory hyperinsulinemia. Conversely, IGF-1 increases insulin sensitivity. However, in acromegaly, increased IGF-1 levels are unable to overcome the insulin-resistant state caused by GH excess.