Tìm hiểu về Sinh lý nội tiết

SINH LÝ NỘI TIẾT 	Arnold A Berthold (1803-1861) In one of the first endocrine experiments ever recorded, Professor Arnold A. Berthold of Gottingen did a series of tests on roosters in 1849 while he was curator of the local zoo. Ablation and replacementBethold found that a rooster's comb is an androgen-dependent structure. Following castration, the comb atrophies, aggressive male behavior disappears, and interest in the hens is lost.Importantly, Berthold also found that these castration-induced changes could be reversed by administration of a crude testicular extract (or prevented by transplantation of the testes).Claude Bernard(1813-1878)Claude Bernard stated that the endocrine system regulates the internal milieu of an animal. The “internal secretions” were liberated by one part of the body, traveled via the bloodstream to distant targets cells. Circa 1854Bernard's charge was to demonstrate that medicine, in order to progress, must be founded on experimental physiology. Endocrine system maintains homeostasisThe concept that hormones acting on distant target cells to maintain the stability of the internal milieu was a major advance in physiological understanding. The secretion of the hormone was evoked by a change in the milieu and the resulting action on the target cell restored the milieu to normal.The desired return to the status quo results in the maintenance of homeostasis Charles Edouard Brown-Séquard (1817-1894) Brown-Sequard further piqued mainstream scientific interest in the chemical contents of the testes with his famous auto-experimentation. On June 1, 1889, before the Sociète de Biologic in Paris, Brown-Sequard reported that he had increased his physical strength, mental abilities and appetite by self-injection with an extract derived from the testicles of dogs and guinea pigsAlthough never substantiated, this claim prompted researchers around the world to pursue the new field of organotherapy Ernest Henry Starling (1866-1927)Besides "his" law of the heart, Starling discovered the functional significance of serum proteins. In 1902 along with Bayliss he demonstrated that secretin stimulates pancreatic secretion. In 1924 along with E. B. Vernay he demonstrated the reabsorption of water by the tubules of the kidney.He was the first to use the term hormoneJim Ferguson1947-2002Famous cardiovascular physiologistTruly understood “Starling’s Law”Disputed that the main purpose of the cardiovascular system was to deliver hormones. 	Locations of major endocrine glandsDeficiency of growth hormone early in life leads to pronounced inhibition of longitudinal growth, resulting in dwarfism. The interrelationship between the pituitary and the thyroid is demonstrated by the concomitant hypothyroidism secondary to deficiency of thyrotropic hormone. Therefore, growth is not only stunted but the development of secondary ossification centers is noticeably delayed, and the epiphysial and apophysial growth plates remain open late in adult life, although they do ultimately close in old age. The cranial sutures remain widely open into adult age. The sella turcica may show widening, if the tumor was intersellar, or an aperture may remain on the floor of the endocranial bones. The skeleton is gracile in dimensions, the cortices are thin, and the spongiosa porotic and sparse. Although growth plates may remain, the metaphysial surface is usually closed by a thin layer of bone, an indication of arrested growth. Adrenocorticotropic Hormone(ACTH) controls secretion of certain hormones from adrenal cortexAdrenal gland stimulating hormone (Cushing's Disease)          (ACTH)        widened face with acne and flushing        fatty deposits over back of neck        stretch marks, easy bruising, hair growth        diabetes mellitus        muscle loss and fatigue        depression and psychosisNelson's syndrome with excessive pigmentation of the skin due to ACTH stimulation of the melanocytes in the skinCushing's disease: medical treatment for tumors which cause the over secretion of corticosteroids by the adrenal glands is unsatisfactory because of their side effects and response rates. Two classes of medication are used: those which interfere with the production of steroids in the adrenal glands and those which act within the brain. Removal of the adrenal glands is an option when pituitary surgery and medical measures fail to control Cushing's disease. This may lead to rapid growth of the pituitary tumor and massive blood levels of ACTH. ACTH stimulates melanin production in the skin, darkening the skin color. This is termed Nelson's syndromeThyroid gland. A.) Consists of 2 lobes connected anteriorly by an isthmus. B.) Follicular cells secrete thyroid hormones. Simple Goiter This condition is characterized by an enlargement of the entire gland, or of one of its two lobes, caused by a deficiency of iodine in the diet. The disease is especially apt to appear in adolescence. Simple goiter occurs in inland areas of all continents. It was common in what was at one time referred to as the goiter belt of the U.S., which includes the Great Lakes region and inland mountain areas. The administration of iodine, or of the iodine-containing hormone thyroxine, effectively prevents the disease. Prevention requires taking small doses of iodine for long periods. Ingestion of iodine during pregnancy prevents development of the disease in the infant as well as in the mother. Public health measures, including the addition of iodine to water supplies and to table salt, have helped to reduce the incidence of simple goiter in certain areas. Iodine is most effective when administered to children who have the disease. Thyroidectomy, or surgical removal of the gland, may be necessary in cases in which the gland has become greatly enlarged. Toxic Goiter This disease, also called exophthalmic goiter, hyperthyroidism, thyrotoxicosis, or Graves' disease, for the Irish physician Robert James Graves, is caused by an excess of thyroxine secretion. The cause of the excessive secretion is obscure. In some cases it may result from excessive stimulation by the pituitary gland. The symptoms of toxic goiter may include a rapid heartbeat, tremor, increased sweating, increased appetite, weight loss, weakness, and fatigue. Some patients have eye problems, such as staring or protrusion. Thiouracil and iodine are sometimes used in the treatment of toxic goiter, as is irradiation of the gland by radioactive iodine. The parathyroid glands are embedded in the posterior surface of the thyroid gland.Parathyroid hormone (PTH) stimulates bone to release calcium (Ca+2) and the kidneys to conserve calcium. It indirectly stimulates the intestine to absorb calcium. The resulting increase in blood calcium concentration inhibits secretions of PTHAdrenal glands. A.) An adrenal gland consists of an outer cortex and an inner medulla. B.) The cortex consists of the three layers or zones of cells.Negative feedback regulates cortisol secretion, similar to the regulation of thyroid hormone secretion.The hormone-secreting cells of the pancreas are grouped in clusters, or islets, that are closely associated with blood vessels. Other pencreatic cells secrete digestive enzymes into ducts.Insulin and glucagon function together to help maintain a relatively stable blood glucose concentration. Negative feedback responding to blood glucose concentration controls the levels of both hormones.                                                             In the thymus gland lymphocytes become specialized. The thymus plays an important role in lymphocyte specialization and immunity.Other Hormone-Producing OrgansHeart: atrial natriuretic peptid – stimulates urinary sodium excretionKidneys: secrete red blood cell growth hormone called erythropoietinAdrenalectomySurgical removal of the adrenal glandsExophthalmosAbnormal protrusion of the eyes.GoiterBulge in the neck resulting from an enlarged thyroid gland.Excess hair growth, especially in women.HyperglycemiaExcess blood glucose