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Hormones are produced by various organs and body tissues, but mainly by the endocrine glands, such as the pituitary, thyroid, and gonads (testes and ovaries). Each gland apparently synthesizes several kinds of hormones; the adrenal glands alone produce more than 25 varieties. The total number of hormones is still unknown, but each has its unique function and its own chemical formula. After a hormone is discharged by its parent gland into the capillaries or the lymph, it may travel a circuitous path through the bloodstream to exert influence on cells, tissues, and organs (target organs) far removed from its site of origin.
One of the best-known endocrine hormones is insulin, a protein manufactured by the beta cells of the islands of Langerhans in the pancreas that is important in carbohydrate metabolism. Other important hormones are thyroxine, an iodine-carrying amino acid produced by the thyroid gland; cortisone, a member of the steroid family from the adrenal glands; and the sex hormones, estrogen from the ovaries and androgen from the testes. Certain hormone substances can be synthesized in the laboratory for treatment of human disease. Animal hormones can also be used, as endocrine hormones are to some extent interchangeable among species. Extracts from the pancreas of cattle, for example, enabled diabetes sufferers to live normal lives even before the chemistry of insulin was fully understood.
Endocrine hormone synthesis and secretion is controlled and regulated by a closed-loop system. Negative feedback loops maintain optimal levels of each hormone in the body. If there are abnormally high levels of a hormone in the blood, feedback to the gland responsible for its production inhibits secretion. If there are abnormally low levels, the gland is stimulated to step up production and secretion. In this way a homeostatic balance is maintained. (See also endocrine glands.)
Ectopic hormones present serious problems for patients and add to the complexity of caring for those with certain kinds of neoplastic diseases. These hormones do not respond to the feedback mechanisms that regulate normal hormonal production; hence, surgery and destruction of the tumorous tissue by radiation and chemotherapy are the treatments of choice.
hormoneA biomolecule released by a cell or gland that transfers information and instructions from one group of cells to another.
hormoneadjective Referring to a hormone, hormonal noun Endocrinology A chemical messenger produced in an endocrine gland and released into the circulation to effect a change in a specific target organ; hormones regulate the internal environment, effecting homeostatic control, regulate reproductive processes, and affect mood and behavior Types Steroid hormones–cortisol, estrogen, testosterone; nonsteroid hormones–choleckystokinin, epinephrine, dopamine, insulin, norepinephrine, serotonin, vasopressin. See ACTH, Beef growth hormone, Biological thyroid hormone, Candidate hormone, Designer hormone, Ectopic hormone, Emasculated hormone, Fat mobilizing hormone, FSH, Gonadotropin-releasing hormone, Growth hormone, HCG, LH, LH-RH, Melanocyte-stimulating hormone, Neurohormone, Pheromone, PTH, Somatotropin release-inhibiting hormone, Thyrotropin releasing hormone, TSH. Cf Neurotransmitter.
hormonea chemical that is produced in the body of a plant or animal, sometimes in very small quantities, and which, when transported (usually by the blood stream in animals) to the target site in another part of the organism, elicits a particular response. In animals the ductless glands that secrete hormones are called ENDOCRINE ORGANS. Animal hormones that influence other endocrine glands are called trophins (or tropins) - for example, GONADOTROPHINS. PLANT HORMONES are usually called growth substances.
Patient discussion about Hormone
Q. does the growth hormone have side effects and what are they?
Q. what is the effect of hormones during pregnancy on a woman's temper?
Q. What types of hormonal changes caused by fibromyalgia? Fibromyalgia affects hormones because I feel pain in my back bone. What types of hormonal changes caused by fibromyalgia?