The anterior pituitary gland secretes at least seven polypeptide hormones. Two of these hormones are released by the hypothalamus: somatostatin-releasing hormone which stimulates growth hormone secretion and somato-statin which regulates the release of growth hormone from the anterior pituitary. Growth hormone regulates an individual’s growth. It also increases the heart rate and myocardial contractility. Specific receptors for growth hormone in the myocardium promote cardiac remodel¬ing, increased contractility, and myocytic hypertrophy. Excess growth hormone secretion causes acromegaly. With this disease, the left ventricle mass, stroke volume, and
A. Clinical Features
These features include enlargement of the heart, premature coronary artery disease, congestive heart failure, hyperten¬sion, intraventricular conduction defects, and cardiac arrhythmias. Mild hypertension occurs in more than 50% of patients. Other manifestations include headache; visual field defects (bitemporal hemianopsia); the growth of the hands, feet, and head; coarsening facial features with elongation of the jaw giving a typical lantern-jaw appearance; enlargement of the liver; and glucose intolerance.
Acromegalic cardiomyopathy occurs, albeit rarely. There is myocyte hypertrophy and an increase in the collagen content per gram of heart compared with normal myo¬cardium. The defect in the myocardium causes arrhyth¬mias, which weaken the myocardial force that leads to congestive heart failure. Treatment of patients with somatostatin analogs that inhibit secretion of growth hormone, octreotide and lanreotide, have shown beneficial effects in small studies. In some patients congestive heart failure has been completely controlled. The left ventricle mass index and mean wall thickness have also shown improvement with this therapy. Still, in patients with long-standing acromegaly there is nonreversible interstitial fibrosis with little recovery.

Страницы: 1 | 2