 | Antidiuretic hormone: Encyclopedia - Antidiuretic hormone
Antidiuretic hormone
Antidiuretic hormone (ADH), also known as arginine vasopressin (AVP), is a hormone that is mainly released when the body is low on water; it causes the kidneys to save water by concentrating the urine and is also involved in the creation of thirst.
It is a peptide hormone produced by the hypothalamus, and stored in the posterior part of the pituitary gland.
Antidiuretic hormone - Physiology
Antidiuretic hormone - Control
ADH is activated by "water receptors" in both the extracellular fluid volume and the intracellular fluid volume. In the extracellular fluid the activators are mainly baroreceptors in the veins, atria, and arterioles. In the intracellular fluid the activators are mainly osmoreceptors in the hypothalamus.
Ethanol and caffeine block the release of ADH from the posterior pituitary gland. The resulting decrease in water reabsorption in the kidneys leads to a higher volume of urine output.
Antidiuretic hormone - Actions
ADH acts on three different receptors, termed V1a, V1b and V2. The receptors are differently expressed in different tissues, and exert different actions:
- V1a - vasoconstriction, gluconeogenesis in the liver, platelet aggregation and release of factor VIII and von Willebrand factor.
- V1b - corticotropin secretion from the pituitary gland.
- V2 - control of free water reabsorption in the cortical collecting ducts of the renal medulla. Activation of adenylate cyclase causes a release of aquaporin-2 channels into the luminal membrane of the cells lining the collecting duct. This allows water to be reabsorbed down an osmotic gradient, and so the urine is more concentrated.
Antidiuretic hormone - Structure and relation to oxytocin
ADH is a peptide consisting of nine amino acids (a nonapeptide). The sequence is cysteine - tyrosine - phenylalanine - glutamine - asparagine - cysteine - proline - arginine - glycine. The cysteine residues form a sulfur bridge.
The structure of ADH is very similar to that of oxytocin, also a nonapeptide with a sulfur bridge. ADH and oxytocin are both produced by the hypothalamus and are the only known hormones released by the human posterior pituary. The similarity of the two can cause some cross-reactions: oxytocin has a slight antidiuretic function, and high levels of ADH can cause uterine contractions.
Antidiuretic hormone - Pharmacology
ADH is used therapeutically in various conditions, and its long-acting synthetic analogue desmopressin is used in conditions featuring low ADH, as well as for control of bleeding (in some forms of von Willebrand disease) and in extreme cases of bedwetting by children. Terlipressin and related analogues are used as vasocontrictors in certain conditions.
Vasopressin has also been implicated in playing a positive role in different kinds of memory formation, including delayed reflexes, image, short- and long-term memory, though the mechanism remains unknown. Thus, desmopressin has come to interest as a likely nootropic.
Demeclocycline, a tetracycline antibiotic, is sometimes used to block the action of ADH on the kidney in hyponatremia (low blood sodium levels) due to increased secretion of ADH (SIADH, see below), when fluid restriction has failed. A new class of medication (conivaptan, tolvaptan, relcovaptan, lixivaptan) acts by inhibiting the action of ADH on its receptors (V1 and V2), with tolvaptan acting on V1a and V2 and the remainder mainly on V1a.
Antidiuretic hormone - Role in disease
Decreased ADH release leads to diabetes insipidus, a condition featuring hypernatremia (increased blood sodium content), polyuria (excess urine production) and thirst.
Raised ADH (syndrome of inappropriate antidiuretic hormone) and resultant hyponatremia occurs in brain diseases and conditions of the lungs. In the peri-operative period, the effects of surgical stress and some commonly used medications (e.g. opiates, syntocinon, anti-emetics) lead to a similar state of excess ADH secretion. This may cause mild hyponatraemia for several days.
Hypothalamus: GnRH - TRH - CRH - GHRH - somatostatin | Posterior pituitary: ADH - oxytocin | Anterior pituitary: GH - ACTH - TSH - LH - FSH - prolactin - MSH
Thyroid: T3 and T4 - calcitonin | Parathyroid: PTH | Adrenal medulla: epinephrine - norepinephrine | Adrenal cortex: aldosterone - cortisol | Pancreas: insulin - glucagon | Ovary: estradiol - progesterone - inhibin - activin | Testis: testosterone - AMH | Pineal gland: melatonin
Stomach: gastrin | Duodenum: CCK - GIP - secretin - motilin - VIP | Ileum: enteroglucagon
Categories: Peptide hormones | Posterior pituitary hormones
Other related archivesACTH, AMH, Adrenal cortex, Adrenal medulla, Anterior pituitary, CCK, CRH, Demeclocycline, Duodenum, Ethanol, FSH, GH, GHRH, GIP, GnRH, Hypothalamus, Ileum, LH, MSH, Ovary, PTH, Pancreas, Parathyroid, Peptide hormones, Pineal gland, Posterior pituitary, Posterior pituitary hormones, Stomach, T3 and T4, TRH, TSH, Terlipressin, Testis, Thyroid, VIP, activin, adenylate cyclase, aldosterone, amino acids, anti-emetics, aquaporin, arginine, arterioles, asparagine, atria, baroreceptors, brain, caffeine, calcitonin, conivaptan, corticotropin, cortisol, cysteine, desmopressin, diabetes insipidus, enteroglucagon, epinephrine, estradiol, extracellular fluid, factor VIII, gastrin, glucagon, gluconeogenesis, glutamine, glycine, hormone, hypernatremia, hyponatremia, hypothalamus, inhibin, insulin, intracellular fluid, kidneys, lungs, melatonin, motilin, new, nootropic, norepinephrine, opiates, osmoreceptors, oxytocin, peptide, peptide hormone, phenylalanine, pituitary gland, platelet, polyuria, posterior part, progesterone, prolactin, proline, receptors, renal medulla, secretin, sodium, somatostatin, sulfur bridge, syndrome of inappropriate antidiuretic hormone, syntocinon, testosterone, thirst, tyrosine, urine, vasoconstriction, vasocontrictors, veins, von Willebrand disease, von Willebrand factor, water
 Adapted from the Wikipedia article "Antidiuretic hormone", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki |
