What are the functions of Growth Hormone (GH)?

From the Guidelines

Growth hormone (GH) plays a crucial role in stimulating growth, regulating metabolism, and maintaining overall health throughout life. The functions of GH can be overviewed as follows:

• Stimulating growth in children and adolescents by promoting cell reproduction and regeneration, particularly in bones and skeletal muscles 1
• Maintaining tissue and organ health by regulating metabolism in adults, including increasing protein synthesis, enhancing fat breakdown (lipolysis), and reducing glucose utilization while maintaining blood glucose levels 1
• Supporting immune function, promoting calcium retention for bone density, and contributing to cardiovascular health by maintaining heart muscle 1
• Influencing psychological well-being and cognitive function, with the pituitary gland releasing GH in pulsatile patterns, peaking during sleep and in response to exercise, stress, and low blood glucose 1

The use of GH therapy is recommended for children with chronic kidney disease (CKD) who have persistent growth failure, defined as a height below the third percentile for age and sex and a height velocity below the twenty-fifth percentile, once other potentially treatable risk factors for growth failure have been adequately addressed 1. GH therapy should be given at dosages of 0.045–0.05 mg/kg per day by daily subcutaneous injections until the patient has reached their final height or until renal transplantation. Additionally, GH therapy may be beneficial for individuals with cystic fibrosis, as it has been shown to improve pulmonary function and growth parameters 1. However, careful monitoring is required due to potential side effects, including glucose intolerance, fluid retention, and joint pain 1.

From the FDA Drug Label

Growth and metabolism of epiphyseal plate cells are directly stimulated by GH and one of its mediators, IGF-I. Serum levels of IGF-I are low in children and adolescents who are GHD, but increase during treatment with somatropin. In pediatric patients, new bone is formed at the epiphyses in response to GH and IGF-I. This results in linear growth until these growth plates fuse at the end of puberty B) Cell Growth: Treatment with somatropin results in an increase in both the number and the size of skeletal muscle cells. C) Organ Growth: GH influences the size of internal organs, including kidneys, and increases red cell mass.

The main functions of growth hormone include:

• Stimulating skeletal growth by promoting the growth of epiphyseal plate cells
• Increasing cell growth by raising the number and size of skeletal muscle cells
• Influencing organ growth by affecting the size of internal organs, such as the kidneys, and increasing red cell mass
• Regulating protein metabolism by stimulating protein synthesis
• Modulating carbohydrate metabolism by affecting insulin sensitivity and glucose levels
• Influencing lipid metabolism by promoting lipid mobilization and reducing body fat stores
• Affecting mineral metabolism by increasing serum levels of inorganic phosphorus and retaining total body potassium
• Stimulating connective tissue metabolism by promoting the synthesis of chondroitin sulfate and collagen 2 2

From the Research

Functions of Growth Hormone

• Growth hormone (GH) plays a crucial role in regulating carbohydrate and lipid metabolism via complex interactions with insulin and insulin-like growth factor-1 (IGF-1) 3
• GH regulates tissue and body growth, and its secretion is reduced in adulthood and aging, but increases in situations of metabolic stress such as prolonged food restriction, hypoglycemia, exercise, pregnancy, and obesity 4
• GH has various physiological functions, including:
  • Increasing hunger perception and food intake
  • Fat mobilization and blood glucose levels
  • Insulin resistance and energy expenditure
  • Neuroendocrine responses during metabolic challenges 4
• GH-induced anabolism is achieved by stimulating amino acid incorporation into protein, reducing oxidative loss, and enhancing lipid utilization 5
• GH replacement therapy has been shown to be safe and effective in adults with GH deficiency, reversing clinical symptoms such as increased adiposity, reduced lean mass, and impaired physical and psychological function 5

Metabolic Effects of Growth Hormone

• GH has a key role in controlling tissue and body growth, and its metabolic effects are mediated through IGF-1 3, 6
• Recombinant human IGF-1 (rhIGF-1) has a dichotomous insulin-like and GH-like action, increasing total insulin sensitivity and stimulating whole body protein synthesis 6
• GH and IGF-1 have a synergistic effect on protein anabolism, improving total nitrogen retention in calorically deprived subjects 6

Growth Hormone and Insulin-Like Growth Factor-1

• IGF-1 therapy has been evaluated for more than two decades in patients with severe primary IGF-1 deficiency, with variable height outcomes 7
• rhIGF-1 offers promise in the treatment of selective growth disorders and in protein catabolic and insulin-resistant states 6