GH, short for growth hormone, is a peptide hormone. It can signal directly via its receptor or indirectly through insulin-like growth factor 1 (IGF-1) stimulation. GH is crucial for its anabolic effects on muscle and bone, and also has distinct metabolic effects in multiple tissues. It is closely associated with processes like aging, and its levels decline with age while its action negatively correlates with lifespan. Genetic models, such as knockout mice, are valuable in understanding its functions [1].

GH-/-mice, created by targeted disruption of the GH gene, have severely decreased IGF-1 levels, small body size, and increased adiposity. They are extremely insulin-sensitive but glucose-intolerant, with a dramatic reduction in pancreatic islet size. GH gene disruption also has profound and depot-specific effects on white adipose tissue (WAT), with subcutaneous WAT having larger adipocytes and reduced fibrosis. These mice are responsive to GH treatment, as shown by changes in serum IGF-1 levels, body parameters, and insulin sensitivity [2].

In conclusion, GH is essential for muscle and bone anabolism, as well as having metabolic effects. The study of GH-/-mice has provided insights into its role in body composition, insulin sensitivity, and adipose tissue characteristics, which may be relevant for understanding aging-related musculoskeletal diseases and metabolic disorders [1,2].