Antidiuretic hormone

Antidiuretic hormone, also called vasopressin, is a peptide hormone that increases water reabsorption in kidney collecting ducts and can constrict blood vessels.

Vasopressin V2 receptor: A G protein-coupled receptor that mediates vasopressin’s water-conserving effects in kidney collecting ducts. Binding this receptor starts the principal-cell signaling pathway that increases water permeability.
Hypothalamus: A brain region that coordinates endocrine, autonomic, and homeostatic functions. Hypothalamic neurons synthesize vasopressin and monitor signals that regulate its release.
Central diabetes insipidus: A disorder in which inadequate vasopressin secretion causes excessive dilute urine and thirst. It demonstrates the consequences of insufficient hormone production or release.
Oxytocin: A hypothalamic peptide hormone released by the posterior pituitary that supports childbirth and milk ejection. It is structurally related to vasopressin but has distinct principal physiological effects.
Aquaporin 2: A water-channel protein inserted into the apical membrane of collecting-duct principal cells in response to vasopressin. Vasopressin raises water reabsorption by moving this channel to the cell surface.
Posterior pituitary: The neural lobe of the pituitary gland, which stores and releases hormones made in the hypothalamus. It releases vasopressin into the bloodstream when hypothalamic neurons signal.
Nephrogenic diabetes insipidus: A disorder in which the kidneys respond inadequately to vasopressin, causing excessive dilute urine. It results when collecting ducts cannot respond normally to the hormone.
Vasopressin V1a receptor: A vasopressin receptor subtype that mediates vascular smooth-muscle contraction and other effects. Unlike the kidney’s V2 pathway, this receptor chiefly links vasopressin to vasoconstriction.
Collecting duct: The final kidney tubule segment where urine concentration is adjusted before fluid enters the renal pelvis. This is the principal site where vasopressin increases water reabsorption.
Osmoreceptor: A sensory cell that detects changes in the concentration of dissolved particles in body fluids. Hypothalamic osmoreceptors help trigger vasopressin release when plasma becomes concentrated.

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