EFFECTS OF GROWTH-HORMONE ON PHOSPHOCALCIUM HOMEOSTASIS AND BONE METABOLISM

In this review the effects of growth hormone (GH) on phosphocalcium ho meostasis and bone metabolism are reported. Some in vitro effects of G H on chondrocytes and osteoblasts are discussed too. The main GH effec ts on phosphocalcium homeostasis are the permissive action on renal 1 alpha-hydroxylase activity by the hypophosphatemic stimulus and the an tiphosphaturic effect by the stimulation of the maximum rate of renal tubular reabsorption of phosphate. On bone, GH is able to stimulate bo ne turnover and to increase bone mass. In addition, GH stimulates type I and type III collagen metabolism. In vitro, GH increases the prolif eration of chondrocytes from the human growing cartilage together with the levels of interleukin-6 in the supernatant. The hormone increases also the proliferation of the human osteosarcoma-derived osteoblastli ke cells and augments the osteocalcin levels in the supernatant. Thus, GH markedly influences phosphocalcium homeostasis and bone metabolism in childhood and adolescence. In addition, it is possible that GH con tinues to play a role in bone physiology during adulthood when final h eight is reached.