Endocrinology is the section of medical science that studies the structure, function, diseases of the internal secretion - the endocrine organs. Word of endocrinology occurred from the Greek words endo - within, krino - allocate and logos - teaching.
The cells of the endocrine glands produce juice (secret glands), which contain specific for each endocrine organ substances called hormones and release them directly into the bloodstream. This is how they differ from exocrine glands that secrete his secret to the duct leaving the outer surface of the body (saliva, sweat glands, cancer of stomach, lung).
Hormone - a chemical that enters the bloodstream and the blood reaches the various organs, where it stimulates or reduces the activity of other cells, called target cells. Through the target cell hormones have an effect on almost all the vital functions of the human body.
By the glands of internal secretion of the body (endocrine glands) are:
pancreas (the insula part) of iron
testes (testicles) in men
ovaries in women
Besides producing hormones and organs other than the endocrine glands. This is the heart, liver and brain.
Currently there are more than 60 different hormones. Most hormones can not be postponed or stock up in the body. The only exceptions are thyroglobulin in the thyroid gland, which supplies enough for two days, and vitamin D, which can be stored in the liver. Therefore, for the normal existence of the human body production of hormones should be carried out continuously. The amount of hormones produced by endocrine glands (endocrine glands) depends on time of day, sleeping or waking, age, mental and physical condition of man.
Some hormones enter the bloodstream in a pulsed mode - portions. Of the sites of synthesis of hormones are transported to the target cells from the bloodstream. Some hormones are transported by joining special transport carrier proteins.
Hormones are excreted in small amounts in unchanged form in bile and urine, and the bulk of them is recycled in the liver and excreted in the bile.
The main center that regulates hormone production and release of the endocrine glands into the blood, is the hypothalamus, located in the brain. It formed hormone-liberiny that stimulate other central endocrine organ - the pituitary gland. In the pituitary gland under the influence of the hypothalamus produced liberinov own hormones - tropanes, which stimulate the production of hormones by endocrine glands. It is these hormones - hormones of the endocrine glands - are the main active link in the chain. In turn, the hormones of the endocrine glands have the opposite effect on the hypothalamic-pituitary system. As the concentration of the hormone in the blood decreases the amount of liberinov in the hypothalamus, then they regulate tropine in the pituitary gland and ultimately reduces production of the hormone that regulates itself so their products.
This feedback circuitry does not describe all the complex regulation of hormones in the body, because it has a huge number of important factors. If necessary, the regulation of hormones and their action is very fast.
Dysfunction of the hormones in the body can be caused by the following reasons: Hormone deficiency. Occurs with a decrease in production of hormones of the endocrine glands, for various reasons: infection, heart attacks, autoimmune processes, tumors, hereditary disease.
The excess of the hormone. Occurs when excessive production and release of hormones into the bloodstream. The reasons may be excessive synthesis of hormones of the endocrine glands, hormone production in other tissues (usually malignant degeneration), increased production of hormones from the tissues of his predecessor, and iatrogenic causes, when the hormone excess is introduced in the appointment of hormones as the drug.
Synthesis of abnormal hormone endocrine glands. Most often this occurs in congenital genetic anomalies.
Resistance to the hormones. In this tissue does not give the usual reaction to a normal or increased amounts of the hormone in the blood. Resistance (immunity) of the tissues to the hormone has a variety of reasons: the hereditary nature of the defect tissue receptors, the appearance of antibodies to hormones.
There are many diseases at once affecting endocrine organs (Schmidt's syndrome, multiple endocrine neoplasia - MEN, lipodystrophy). This makes diagnosis and treatment of endocrine diseases more difficult.