Question

explain growth hormone and melatonin in your own words

at least 10 sentences each growth hormone and melatonin.

Answer 1

Growth hormone (GH) or somatotropin, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals, thus being important in human development. GH is a 191-amino acid, single-chain polypeptide which is synthesized, stored and secreted by somatotropic cells of the anterior pituitary gland. Effects of growth hormone on the tissues of the body is generally anabolic. It is a type of mitogen which is specific only to the receptors on certain types of cells, GH acts by interacting with a specific receptor on the surface of cells. A number of factors are known to affect GH secretion in humans, such as age, sex, diet, exercise, stress, and other hormones. Increased height during childhood is the most widely known effect of GH. In addition to increasing height in children and adolescents, growth hormone has many other effects on the body like, increase in calcium retention, strengthening and increase in the mineralization of bone, increase in muscle mass through sarcomere hypertrophy, promoting lipolysis, increased protein synthesis etc. GH excess in childhood causes gigantism. A prolonged GH over-secretion in adults, thickens the bones of the jaw, fingers and toes, resulting heaviness of the jaw and increased size of digits, known as acromegaly. Major manifestations of GH deficiency in children are growth failure, development of a short stature, and delayed sexual maturity. In adults, this deficiency results in weaker bones that are more prone to pathologic fracture and osteoporosis.

Melatonin is a hormone which regulates the sleep–wake cycle. It is primarily released by the pineal gland. In vertebrates, melatonin secretion is regulated by activation of the beta-1 adrenergic receptor by norepinephrine. Blue light (460–480 nm), suppresses melatonin biosynthesis (which is proportional to the light intensity and length of exposure). Production of melatonin again begins in the evening at the point called the dim-light melatonin onset. Melatonin has quite a few functions in the human body : maintenance of Circadian rhythm as it plays an important role in the regulation of sleep–wake cycles; it acts as an antioxidant in vitro, where melatonin acts as a direct scavenger of oxygen radicals and reactive nitrogen species (via signal transduction through melatonin receptors, melatonin promotes the expression of antioxidant enzymes such as superoxide dismutase, glutathione peroxidase, glutathione reductase, and catalase); melatonin also occurs at high concentrations within mitochondrial fluid which greatly exceed the plasma concentration of melatonin; it also has a role in the immune system as it has an anti-inflammatory effect.