Human growth hormone (HGH), a remarkable protein hormone consisting of 190 amino acids, plays a crucial role in the body’s development. Synthesized and secreted by the Somatotroph cells, also known as Somatotropin, in the anterior pituitary, HGH holds significant potential for various physiological processes. The genes responsible for producing human growth hormone are localized in the q22-24 region of chromosome 17. Structurally, HGH comprises four helices that facilitate its functional interaction with the GH receptor. Interestingly, HGH exhibits structural similarities to prolactin and chorionic somatomammotropin, suggesting an evolutionary connection between the three hormones. This trio is known to promote growth and facilitate lactogenic activity.
Controlling Human Growth Hormone Secretion
The synthesis and secretion of HGH are regulated by multiple factors, including exercise, nutrition, sleep, stress, and sometimes even by the hormone itself. However, the control largely lies in the hands of two hypothalamic hormones, Growth hormone-releasing hormone (GHRH) and Somatostatin (SS), as well as a stomach hormone called Ghrelin.
The Multifaceted Functions of HGH
Human growth hormone contributes significantly to the development of the human body. It exerts two distinct types of effects on human tissues and the overall system: direct and indirect. Direct effects occur when growth hormone binds to its receptors on target cells. On the other hand, indirect effects are stimulated by insulin-like growth factor-I (IGF-I), a hormone secreted by the liver and other tissues in response to growth hormone activity. In fact, most of the growth-promoting effects of HGH are mediated by IGF-I acting on target cells.
Thus, it becomes evident that HGH, also known as Somatotropin, plays a vital role in major physiological processes such as growth and metabolism.
HGH and its Impact on Growth
The primary function of growth hormone in promoting body growth is to stimulate the liver and various tissues to secrete IGF-I. This, in turn, triggers the proliferation of chondrocytes (cartilage cells), leading to bone growth.
HGH and its Influence on Metabolism
Human growth hormone has been found to exert significant effects on protein, lipid, and carbohydrate metabolism. These effects can be direct, indirect, or a combination of both.
Beyond height growth, HGH fulfills a range of specific and essential functions. These functions encompass protein synthesis, muscle mass development, calcium retention, bone mineralization, immune system stimulation, and fuel homeostasis maintenance, among others.
This comprehensive understanding of human growth hormone reveals its vast potential. The advent of biosynthetic human growth hormone, also known as recombinant human growth hormone (rHGH), in 1985 revolutionized its therapeutic use in the United States. Since then, biosynthetic HGH has largely replaced pituitary-derived human growth hormone, particularly in medical applications.