Direct Action of GH

Growth hormone (GH) has long been known to have a pivotal role in the regulation of somatic growth. Thus, GH deficiency results in proportionate dwarfism that is responsive to replacement therapy with GH. The physiological mechanism(s) by which GH exerts its stimulatory effect on somatic growth has not yet been elucidated. It has been demonstrated convincingly that administration of GH stimulates the growth of cartilage and other tissues by increasing the number of cells, showing that the effect of GH in vivo ultimately results in a stimulation of DNA synthesis and cell proliferation (1-3). However, efforts to demonstrate stimulatory effects of GH in vitro in explants of cartilage and other skeletal tissues have been unsuccessful in most cases.