Russian

HORMONES

Hormones are regulatory substances in complex organisms. They are formed in specialized cells and released in small quantity (internal secretion). Then they are transported along the organism and specifically operate functions of other cells or organs far from the place of their formation. The following glands of internal secretion are known in a human organism: hypophysis-hypothalamus system, epiphysis, thyroid gland, parathyroid glands, Langerhans islets in the pancreatic gland, suprarenal glands (adrenal cortex and adrenal medulla), sex glands (ovaries, spermaries) and placenta. Hormones are divided into two large groups, polypeptides and steroids.

The major representatives of the first group of hormones are the following proteins:
- thyreoglobulin (the protein of the thyroid gland), which contains iodized amino acid thyroxine;
- insulin, the gormon, which is synthesized in Langerhans islets of the pancreatic gland and regulates sugar rate in blood;
- oxytocin and vasopressin, the hormones of the posterior lobe of hypophysis (the first one causes uterus
involution, the second one raises blood pressure);
- melanocyte-stimulating hormone, which is produced by the intermediate lobe of hypophysis; it causes growth of pigmentation;
- corticotrophin, the hormone of the anterior lobe of hypophysis; it is important for fight against arthritis.

Other hormones of the anterior lobe of hypophysis, such as thyreotropic hormone, prolactin, somatotropin (growth hormone), gonadotropin, and others are proteinaceous.

The second group of hormones are steroid hormones. They include sex hormones (estrone, progesterone, testosterone, androsterone, and the hormone of the adrenal cortex, cortisone). The hormone of suprarenal glands, adrenaline, which raises blood pressure and stimulates cordial activity, also belongs to this group.

Hormonal activity is defined by chemical functionality of the atomic groups, which are few in number. Chemical difference between testosterone and cortisone are little, but their physiological functions are absolutely different.