Growth Hormone and Skeletal Muscle Function

Abstract

It is well established that skeletal muscle is a target tissue for GH, and there is a wealth of literature concerning the influence played by GH on the musculoskeletal system. It is now widely recognized that GH-Insulin-like growth factor-I (IGF-I) axis has an important role in controlling the growth and differentation of skeletal muscle. Recently, this topic was extensively reviewed by Florini et al (1). As early as 1934, it was reported that administration of anterior pituitary extracts in rats increases muscle mass (2). These observations were confirmed by Plattener and Reed (3), who found that, in rats, treatment with “anterior pituitary growth factor” leads to an increase in muscle mass, but does not affect muscle performance. Accordingly, rats treated with 500 µg GH/day for 3 weeks gained significantly more than controls, and their quadriceps muscles were 15-40% heavier, although muscle performance did not change (4). In hypophysectomized animals GH administration has induced an increase in muscle mass and activity of polyribosomes, indicative of enhanced muscle protein synthesis (5). The strong link between GH and skeletal muscle growth has been convincingly demonstrated by Palmer et al (6) who provided clear evidence that intact rats treated with a polyclonal antiserum to rat GH exhibit a marked reduction in weight, total protein and RNA content of hind limb muscle. Futhermore, it is also well known that hypophysectomized rats have a decrease in the levels of mRNA for all forms of myosin heavy chain (MCH) that is partially remedied by GH (7). The mode of action on skeletal muscle, however, still remains unclear. Although, the somatomedin hypothesis implies that many of the biological activities of GH are mediated by IGFs, which could regulate the proliferation and differentiation of skeletal muscle cell, a direct effect of GH on muscle cannot be excluded.KeywordsGrowth HormoneGrowth Hormone DeficiencyHuman Growth HormoneMuscle Protein SynthesisGrowth Hormone TreatmentThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.