Hormone posterior pituitary

Anterior pituitary hormones, Anterior pituitary-like hormones. Posterior pituitary hormones. Human growth hormone. 

Hypothalamo-pituitary function Anterior pituitary hormones Posterior pituitary hormones Adrenal cortex Adrenal medulla Thyroid Pancreas INTRODUCTION... 

HORMONES - ESTROGENS AND ANTIESTROGENS] (Vol 13) Hormones Posterior Pituitary Hormones... 

Spatola AF (1995) Hormones (posterior pituitary hormones). Kirk—Othmer Encyclopedia of Chemical Technology, 4th edn, Vol 13. Wiley, New York, pp 391-406. 

Thyroid-stimulating hormone Posterior pituitary TSH Thyroid gland Secretion of thyroid hormones... 

The posterior lobe of the pituitary, ie, the neurohypophysis, is under direct nervous control (1), unlike most other endocrine organs. The hormones stored in this gland are formed in hypothalamic nerve cells but pass through nerve stalks into the posterior pituitary. As early as 1895 it was found that pituitrin [50-57-7] an extract of the posterior lobe, raises blood pressure when injected (2), and that Pitocin [50-56-6] (Parke-Davis) causes contractions of smooth muscle, especially in the utems (3). Isolation of the active materials involved in these extracts is the result of work from several laboratories. Several highly active posterior pituitary extracts have been discovered (4), and it has been deterrnined that their biological activities result from peptide hormones, ie, low molecular weight substances not covalendy linked to proteins (qv) (5). 

The principal hormones of the human posterior pituitary include the two nonapeptides, oxytocin [50-56-6] and arginine vasopressin [11000-17-2] (antidiuretic hormone, ADH). Many other hormones, including opioid peptides (see Opioids, endogenous), cholecystokinin [9011-97-6] (CCK) (see Hormones, BRAIN oligopeptides), and gastrointestinal peptides, also have been located in mammalian neurohypophysis (6), but are usually found in much lower concentrations (7). Studies have demonstrated that oxytocin and vasopressin are synthesized in other human organs, both centrally and peripherally, and there is considerable evidence for their role as neurotransmitters (see Neuroregulators) (8). 

Synthesis of Posterior Pituitary Hormones and Their Analogues... 

In humans, the hypothalamic-derived protein and the hormone noncovalent complexes are packaged in neurosecretory granules, then migrate along axons at a rate of 1 4 mm/h until they reach the posterior pituitary where they are stored prior to release into the bloodstream by exocytosis (67). Considerable evidence suggests that posterior pituitary hormones function as neurotransmitters (68) vasopressin acts on the anterior pituitary to release adrenocorticotropic hormone [9002-60-2] (ACTH) (69) as well as on traditional target tissues such as kidneys. Both hormones promote other important central nervous system (CNS) effects (9,70). 

SUM MARY DRUG TABLE ANTERIOR AND POSTERIOR PITUITARY HORMONES... 

There may be a decreased resistance and inability to The posterior pituitary gland produces two hormones localize infection. The nurse observes the skin daily for vasopressin (antidiuretic hormone) and oxytocin (see localized signs of infection, especially at injection sites Chap. 53). Posterior pituitary hormones are summarized or IV access sites. Visitors are monitored to protect the in the Summary Drag Table Anterior and Posterior patient against those witii infectious illness. Pituitary Hormones. 

Vasopressin (Rtressin Synthetic) and its derivatives, namely lypressin (Diapid) and desmopressin (DDAVP), regulate the reabsorption of water by the kidneys. Vasopressin is secreted by the pituitary when body fluids must be conserved. An example of this mechanism may be seen when an individual has severe vomiting and diarrhea with little or no fluid intake. When this and similar conditions are present, die posterior pituitary releases the hormone vasopressin, water in die kidneys is reabsorbed into die blood (ie, conserved), and die urine becomes concentrated. Vasopressin exhibits its greatest activity on die renal tubular epithelium, where it promotes water resoqition and smooth muscle contraction throughout die vascular bed. Vasopressin has some vasopressor activity. 

The posterior pituitary is innervated by direct nervous stimulation from the hypothalamus, resulting in the release of specific hormones. The hypothalamus synthesizes two hormones, oxytocin and vasopressin. These hormones are stored in and released from the posterior pituitary lobe. Oxytocin exerts two actions (1) it promotes uterine contractions during labor, and (2) it contracts the smooth muscles in the breast to stimulate the release of milk from the mammary gland during lactation. Vasopressin is an antidiuretic hormone (ADH) essential for proper fluid and electrolyte balance in the body. Specifically, vasopressin increases the permeability of the distal convoluted tubules and collecting ducts of the nephrons to water. This causes the kidney to excrete less water in the urine. Consequently, the urine becomes more concentrated as water is conserved. 

In contrast to the posterior pituitary lobe, the anterior pituitary lobe is under the control of several releasing and inhibiting hormones secreted from the hypothalamus via a portal vein system. The anterior pituitary lobe, in turn, synthesizes and secretes six major hormones. Figure 43-1 summarizes the physiologic mediators and effects of each of these hormones. 

Vasopressin is a peptide hormone produced by the hypothalamus and secreted by the posterior pituitary in response to stimulation. Normal stimuli for vasopressin release are hyperosmolarity and hypovolemia, with thresholds for secretion of greater than 280 mOsm/kg and greater than 20% plasma volume depletion. A number of other stimuli, such as pain, nausea, epinephrine, and numerous drugs, induce release of vasopressin. Vasopressin release is inhibited by volume expansion, ethanol, and norepinephrine. The physiological effect of vasopressin is to promote free water clearence by altering the permeability of the renal collecting duct to water. In addition, it has a direct vasoconstrictor effect. Consequently, vasopressin results in water retention and volume restoration. In patients with septic shock, vasopressin is appropriately secreted in response to hypovolemia and to elevated serum osmolarity (R14). 

The hypothalamic releasing factors regulate release of the anterior pituitary trophic hormones. As summarized in Figure 52-1, the releasing factors are produced in various neuronal groups within the hypothalamus and are transported to the median eminence for release into the portal circulation to the anterior pituitary. Neurons in the hypothalamus also produce the hormones oxytocin and vasopressin, which are released by the posterior pituitary into the blood. Therefore, it is not surprising that behavior and experience, which influence the hypothalamus, sometimes alter the secretion of these hypothalamic releasing factors and hormones. 

Neuropeptides are often grouped by their structural similarity or tissue source. Among these are the hypothalamic releasing factors (e.g., corticotrophin-releasing factor [CRF], thyrotropin-releasing hormone), anteior pituitary hormones (e.g., adrenocorticotrophic hormone [ACTFI], follicle-stimulating hormone [FSFI]), and posterior pituitary hormones... 

Plasma prolactin levels are reduced with acute treatment and remain suppressed after 28 days of chronic treatment (Murphy et al. 1998). With acute treatment, no effects are seen on plasma luteinizing hormone or testosterone levels. However, chronic dietary 5% ginseng increases testosterone levels in male rats (Fahim et al. 1982). Chronic ginsenosides do not alter posterior pituitary hormones oxytocin and vasopressin (Zierer 1991). Similarly, human males administered ginseng extract showed an increase in plasma testosterone, dihydrotestosterone, follicle-stimulating hormone, and luteinizing hormone, but a decrease in prolactin (Salvati et al. 1996). 

Zierer R. (1991). Prolonged infusion of Panax ginseng saponins into the rat does not alter the chemical and kinetic profile of hormones from the posterior pituitary. J Ethnopharmacol. 34(2-3) 269-74. 

In heterodetic peptides, the ring system is formed from amides and other heteroatom linkages, for example, a disulfide bridge, a thioether or a lactone linkage. The most common nonamide links in heterodetic peptides are the disulfide bonds (found in posterior pituitary hormones such as oxytocin and vasopressin) and the ester (lactone) fnnction. " ... 

Posterior pituitary Two hormones, vasopressin and oxytocin, are synthesised in the hypothalamus and then transported through nerve axons to the posterior pituitary, where they are stored until released. Vasopressin acts on the kidney to conserve water. Its secretion is stimulated by thirst and a decrease in blood pressure. Secretion of oxytocin initiates uterine contraction for parturition. It also stimulates milk ejection from the mammary glands. 

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