Biochemistry

resulting in a rearrangement of the synthetic activity of the target cell. Thus, the hormonal effect is realized at the level of the target cell genetic apparatus. Biological effects of hormones acting on the cell genetic apparatus, manifests itself mainly in the effect on the growth and differentiation of tissues and organs. Classification of hormones By chemical nature, all hormones can be divided into several groups. The first group includes protein-peptide hormones. These are hormones of the hypothalamus, pituitary , pancreas, parathyroid and thyroid glands, as well as gastrin produced in the stomach. The second group includes hormones that are derivatives of steroids - steroid hormones. These include hormones of the gonads, adrenal cortex, and placenta. The third group consists of hormones - derivatives of amino acids. These are hormones of the adrenal medulla and calcitonin, which is formed in the thyroid gland. Substances exhibiting local hormonal action are distinguished into a separate group: bradykinin, prostaglandins, kallikrein, renin, and others. Peptide hormones cannot penetrate into target cells, but interact with protein receptors; located on the surface of cells in their plasma membrane. As a result, the activity of adenylatccyclase embedded in the same membrane increases, and adenosinemonophosphate is formed, which transmits a hormonal signal to the metabolic systems of the cell. Hormones of the hypothalamus. The hypothalamus secretes hormones that regulate the activity of the pituitary gland. Currently, seven stimulants and three inhibitors of the secretion of pituitary hormones (releasing hormones) are known. Only three were obtained in pure form and their structure was deciphered. These include: a hormone that promotes the release of thyroid- stimulating hormone, a hormone that affects the release of luteinizing hormone, and a hormone that has an inhibitory effect on the release of growth hormone. In addition to these hormones, two more purified preparations were isolated from the hypothalamus that stimulates the release of growth hormone. They differ from each other in specific properties, with almost the same biological activity, as well as molecular weight. The chemical nature of other hormones has not been determined. Pituitary hormones. The pituitary gland produces and releases into the blood a whole group of hormones that affect the growth and development of the body, metabolism and the function of peripheral endocrine glands. Anterior pituitary extracts hypophysiotropic hormones that regulate the activity of other endocrine glands. So, growth hormone (somatotropic hormone, STH) has a wide range of biological effects, affects all cells of the body. It stimulates tissue growth and body size. The molecular basis of this effect is 283