NEW PHYSIOLOGICAL AND PHARMACOLOGICAL ASPECTS OF GROWTH-HORMONE .1. EFFECTS IN ADULTS

Growth hormone (GH), a well-known anabolizing agent, not only plays a physiological role in childhood by promoting longitudinal growth, but also it remains to be secreted during adult life. Many aspects on phys iological and pharmacological actions of this hormone in adulthood hav e been clarified in the last years. GH induces the biosinthesis of ins ulin-like growth factor I (IGF-I), a peptidic compound that acts as a mediator of indirect actions of GH. In GH deficient adults, exogenous GH administration produces a decrease in adipose mass which is accompa nied by an increase in lean body mass, mainly due to an enlargement of muscle cell mass. Sodium and water retention has been also described. An augmentation in muscle strength, basal metabolic rate and nitrogen retention by action of GH are expressions of the potential anabolizin g effects of this hormone in adult life. Glucose tolerance is decrease d by GH, and this effect is accompanied by a decrease in peripheral ut ilization of glucose and an increase in insulin secretion. GH behaves as a lipolytic hormone and gives rise to an increase in resistance to the lipogenetic action of insulin. GH treatment increases plasma level s of bone G1a protein and other marker of osteoblastic activity, what suggests a physiological role of GH in bone turnover regulation. Many other organic functions are also affected by GH administration.