It is important that we check the relationship of GH with some of the peptide factors of growth, especially with the somatomedins. This will allow us to better understand the mechanism of various actions of GH. The initial concept of the endocrine system indicated to us that it was an organized network of glands and ducts into which classic hormones were secreted into the bloodstream, where they would reach distal organs to carry out their function. Now we see it in a wider context that not only includes the initial concept but also the exsistence of a large number of peptidic factors of growth that are produced in many tissues. These factors may work locally in the cells where they originated by means of autocrine mechanisms, or may influence adjacent tissues through paracrine mechanisms. They may also be transported through the blood like classic hormones and work like that through endocrine mechanisms. In many cases, classic hormones (for example, GH) regulate the production of these peptidic factors of growth (for example, somatomedin-C or IGF-I) which, in turn, control cellular proliferation in such a way that these growth factors are the mediators through which GH exercises some of its action on the tissue growth. How was the concept of the exsistence of somatomedins arrived at? Towards the end of the decade of the fifties, Daughaday and Salmon observed that the administration of GH in hypopysectomized rats resulted in an increase in the incorporation of sulfate and thy~midine due to the exsistence of a substance in the serum which was GH-dependent and they called it sulfation factor.  Afterwards, other names like somatomedin-C, insuline-like growth factor (IGF) or insuline-like non-supressable growth factor NSILA) were given to this serum factor. Historically, the term somatomedin (growth mediator) was proposed by the researchers whose line of investigation was somatic growth. In contrast, the name IGF was proposed by researchers in the field of insulin physiology. Even though IGF is structured and biologically related to proinsulin, initial studies showed that similar properties of this peptide to insulin are not neutralized in the presence of good quantities of anti-insulin antibodies; thus the term NSILA. Somatomedin-C is the principal IGF found in human serum and one of the 70 aminoacids synthesized primarily in the liver as well as in the kidneys, heart, mesenchyme and fetal lungs. The production of somatomedin-C is GH dependent, even though, it is also influenced by other factors that can influence, for example, malnutrition and fasting decrease its production. In well-nourished subjects, circulating IGF-I levels are a reflection of GH secretion during 24 hours; its measurement, although complex, is not as high as GH (pulsating character). In contrast to GH, the majority of the quantity of circulating IGF-I is in the form of a complex united to proteins and has a prolonged half-life. The decline in the liberation of GH and, consequently, a decrease in the production of somatomedin-C present in the elderly has, as a consequence, a decline in muscular mass, nitrogen retention, organomegaly and in the thickness of the skin. The preceeding served as a basis for Marcus and collaborators to study the effects of the administration of GH during 7 days in a group of humans older than 60 years of age. They found an increase in the levels of IGF-I, in the retention of nitrogen, phosphate, parahormone, osteocalcin, (OH)2 vitamin D and urinary calcium. There was also a decrease in the secretion of cholesterol and sodium and a moderate alteration in the tolerance to glucose with hyperinsulemia. Rudman and his group studied the effects of the administration of GH for six months in healthy men over the age of 60 whose low levels of IGF-I were similar to those observed in young men. The preceeding resulted in a significant increase in lean body mass (14.4 percent) and a slight decrease in adipose tissue mass (8.8 percent). There was a tendency for the skin to thicken and a minimum increase in bone mass (1.6 percent) was found. They note that in other studies no benefits were found by adding GH in patients with osteoporosis who were being treated with calcitonin. Other studies have also shown that old age is associated with a decrease in the levels of IGF-I nevertheless, when GH is administered to the elderly, IGH-1 increases and the same as when GHRH is administered. These findings suggest that the decrease of IGF-I observed in the elderly reflects a decrease in GH beond that of tissular resistance to the effect of GH. Aging in humans is also associated with a reduction in muscular and bone mass and with an increase in body fat,'' which suggests that the deficiency of GH in the elderly can be partially responsible for these changes in body composition.. On the other hand, the field of homeopathy has also been influenced by the advances in research in the use of GH in the elderly. Based on the preceeding, we designed this study in which mcg of a homeopathic formulation of GH potentized to 30X was used. In another group the same homeopathic formulation was used plus another formulation of "HE" potentized to 3X. In a third group that served as a control, only a placebo was used. The effects of the formulations on the plasmatic levels of somatomedin-C (Sm-C) in the blood chemistry, lipids profile, functional hepatic tests, immunoglobulins, iron and calcium were investigated.