Growth hormone in anti-aging medicine: a critical review

THE SOMATOTROPIC SYSTEMGrowth hormone (GH) is released from the anterior pituitary gland.The secretion of GH is regulated and controlled by the hypothalamus, whereby growth hormone releasing hormone (GHRH) and ghrelin both exercise stimulatory effects and somatostatin inhibitory effects.GH causes insulin-like growth factor-I (IGF-I) synthesis and secretion in the peripheral target organs, whereby systemic measurable IGF-I predominantly originates from the liver.When an organic-related hypopituitarism occurs, the pituitary partial functions exhibit varied sensibility, or are more susceptible to damaging effects.Besides the gonadotropic axis, the somatotropic axis is one of the two partial functions that can fail very early in pituitary disorders, while the thyrotropic and corticotropic and, in particular, the lactotropic axes are much more resistant. CLINICAL ASPECTS OF GROWTH HORMONE DEFICIENCYGH deficiency manifests itself visibly in childhood as proportional dwarfism.In adulthood, increased central adiposity, decreased muscle and bone mass, decreased extracellular fluid volume, disorders of lipid metabolism, restricted endothelial function and negative changes in psychosocial competence are all associated with GH deficiency 1 . EFFECTS OF GROWTH HORMONE REPLACEMENT IN ORGANIC-RELATED GROWTH HORMONE DEFICIENCYOf the numerous therapeutic measures to be considered for pituitary disorders, GH substitution in organic-related hypopituitarism, for example owing to pituitary tumors, post-surgical conditions or radiotherapy, is by no means the most important.Nevertheless, according to criteria of evidence-based medicine it is by far the most studied measure.Evidence on level I (at least one randomized, controlled study) is available for several target parameters (Table 1).Casuistically, it could be shown that GH replacement can lead to a drastic decrease of body fat mass during the course of 6 months of GH replacement therapy 3 .Regarding the portrayal of these changes in controlled studies, the average aim was an increase of 5 kg in lean body mass and a decrease of 5 kg of fat mass, while maintaining a constant body weight 8 .In the data available from application reports (Pharmacia International Metabolic Survey KIMS, unpublished data), there were fewer changes in patients not under strict selection; realistically, a decrease or increase of fat and lean mass by 1.5-2 kg can be expected.The largest study of collection data on fat metabolism comes from an application report.In 1682 patients, who had never been previously