Lavin Chapter 12

Chapter 12 • Growth Hormone in Adults   135

septal thickness and left ventricular diameter mass. After GH administration, there were increases in the left ventricular mass, left ventricular end diastolic volume, and stroke volume. Changes in these parameters may correlate with reported subjective benefits of increased exercise tolerance and energy. F. Results on the impact of IGF-1 in cardiovascular disease , however, are still controversial. XII. CHRONIC FATIGUE SYNDROME Preliminary studies of GH therapy in a subset of patients with chronic fatigue syndrome and GHD have also shown some encouraging results. XIII. ADIPOSE TISSUE Adult GH-deficient patients demonstrate increased fat mass, particularly visceral adiposity, and several studies have shown significant decreases in total body fat content in responwse to GH treatment. These decreases occur in both subcutaneous and visceral fat within 6 months after initiation of therapy. GH administration increases lipolysis. Untreated adults have decreased lean body mass and, with treatment, an increase in muscle mass ensues. XIV. STRENGTH Some studies have shown increases in isometric or isokinetic strength. In other studies, exercise capacity and physical performance were improved by treatment and demon- strated by the facts that VO 2max and maximum work capacity were increased. XV. GH TREATMENT IN THE ELDERLY There are many unanswered questions about the use of GH in the elderly (as well as in adults) with GHD. Currently, research has brought us to an important beginning in deciphering the actions of GH in this age group. Gotherstrom et al. have described a 10-year prospective study of the metabolic effects of GH replacement in adults. There was a sustained reduction of body fat during the study period, sustained improvement in serum lipid profiles, and lowering of hemoglobin A 1c by the end of the study. Their study concludes that a low dose of GH can improve body composition and serum lipid profile without any significant impairment of glucose metabolism. GH replacement should, therefore, be considered in elderly GHD adults. XVI. GH AND DIABETES MELLITUS A. In another study by Gotherstrom looking at GH-deficient adults, the conclusion was that GH did not affect the risk of diabetes mellitus in patients who had normal body mass index. After 10 years of GH replacement in adults, there was no increased incidence of diabetes or malignancy. Contrawise, GH-deficient patients had increased serum insulin concentration and evidence of insulin resistance. Glucose-clamp studies have confirmed these observations. Patients with an excess of GH may also demonstrate insulin resistance. B. In a different study, a low mean dose of GH normalized serum IGF-1 levels and improved body composition in elderly GH-deficient patients without any significant deterioration in glucose homeostasis. XVII. LIPIDS A. GH replacement reduces visceral fat, and total cholesterol and LDL levels may decrease in 10% to 20%. In one review, 63 adults with GHD were assessed after 7 years of treatment. Total cholesterol and LDL decreased and high-density lipoprotein increased, whereas triglyceride concentrations remained unchanged. B. The administration of GH reduces CRP and improves lipoprotein metabolism. Furthermore, GH decreases fat mass and improves insulin sensitivity. XVIII. BONE DENSITY A. Low BMD in adults has been demonstrated in patients with GHD. The age of onset appears to determine the severity of the osteopenia, and the severity of GHD