Lavin Chapter 12

Chapter 12 • Growth Hormone in Adults   139

the symptoms of the disease. At 4 months, the Crohn disease activity index score had decreased significantly in the GH group. This compared with a much smaller decrease in the placebo group. Side effects included some swelling and headache, which usually went away during the first month of therapy. Researchers need to study the effects of GH further with clinical trials to determine its value in treating Crohn disease. D. Low IGF-1 linked to Alzheimer disease: It is widely accepted that the IGF-1 is involved in the body’s aging process. New research suggests that it might also play a role in Alzheimer disease in elderly men. This study showed a significant link between low serum levels of IGF-1 and insulin-like growth factor binding protein 3 in Alzheimer disease in men but not in women. The investigations, therefore, justify a longitudinal study to evaluate these data. E. Cognition: Decreases in GH secretion with age may contribute to cognitive changes associated with aging. In this study, the data confirmed that cognitive performance in elderly males is associated with GH secretion with respect to target detection and speed of responding in conditions of selective attention, short-term memory, and basic processing speed. F. Hearing: The study evaluated a hearing status of GH in adults with isolated GHD belonging to an extended Brazilian kindred with a homozygous mutation in the GH receptor gene. They concluded that compared with controls in the same area, subjects with untreated congenital lifetime idiopathic GHD report more misophonia and dizziness and have a preponderance of mild high-tone sensorineural hearing loss and have an absence of stapedial reflex and other abnormalities. These were reversed with GH treatment. G. Hypopituitary control and complications study: The data from the study con- clude that GH replacement provides sustained improvement in quality of life for up to 10 years. H. Prader–Willi syndrome (PWS) (see Chapter 16): Altered GH secretion has been related to reduced cardiac mass and systolic function compared to controls. They conclude that GH therapy increased the cardiac mass of PWS adults without causing overt abnormalities of systolic and diastolic function. Although the association between lean mass and left ventricular ejection fraction during GH therapy corroborates a favorable systemic outcome of long-term GH treatment in adults with PWS, subtle longitudinal modifications of functional parameters advocate appropriate cardiac monitoring in the long-term use of GH for these patients. Current data suggest that long-term GH administration can favor preservation of cardiac and metabolic parameters in adult PWS patients. GH treatment can be seen as a critical upholder of physiologic homeostasis and could create extended benefits for cardiovascular health in adults with this disorder. I. The anaerobic energy system underpins the initiation of all physical activities, including those of daily living. GH treatment improved sprinting in recreational athletes, a performance measure dependent on the anaerobic energy system. The physiologic and functional link between GH and the anaerobic energy system is unknown. They conclude that GH regulates anaerobic capacity, which determines quality of life and selective aspects of physical function. Strength and endurance are measures of muscle function that depend on muscle size, muscle fiber composition, and the availability of energy to support the exercising muscle. This energy is available as adenosine triphosphate (ATP), which is produced by two complimentary energy systems, one anaerobic (oxygen-independent) and the second aerobic (oxygen-dependent). The amount of preformed ATP present in muscle is sufficient to sustain physical activity for the first 5 to 10 seconds. There- after, anaerobic glycolysis provides energy for an additional 30 to 40 seconds. The aerobic energy system supports endurance exercise, whereas the anaerobic energy system powers intensive activity of short-term duration. The anaerobic energy system supports activities of daily living, such as rising from a chair, climbing stairs, and rushing for a bus. Thus, it is conceivable that impairment of anaerobic capacity leads to the perception of increased fatigue during the execution of ordinary activities of daily living, a symptom commonly observed in adults with GHD.