MODULE SUPPLEMENT: ENDOCRINE SYSTEM
Growth Hormone

Growth hormone is important in the regulation of many physiological processes as outlined in the table below.

Growth hormone has both insulin like and anti-insulin (diabetogenic) effects. It is involved in: skeletal and muscle growth, thus promoting the development of lean body mass and skeletal mass; the regulation of lipolysis or the breakdown of fat; and the cellular uptake of amino acids. It also can increase glomerular filtration rate and renal plasma blood flow. However, it also causes an increase in both blood pressure and blood sugar and can cause diabetes.

The actions of growth hormone are mediated mainly by somatomedin C (known as Insulin like Growth Factor I [IGF-I]) which is secreted by the liver as well as other tissues in response of growth hormone stimulation (Gruenewald & Matsumoto, 1999).

Growth hormone has become an important focus of research in aging because levels of growth hormone decrease significantly with age (Muller, Rigamonti, et al., 2002; Rosen, 2000; Russell-Aulet, Dimaraki, et al., 2001). In adult men, this decline occurs at about 14% per decade so that by the age of 70-80, half have no significant growth hormone secretion during a twenty-four hour period (Gruenwald & Matsumoto, 1999).