Antidiuretic hormone

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Antidiuretic hormone


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Antidiuretic hormone

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An experiment is done to determine the physiology of maintaining normal plasma osmolarity. In the experiment, the plasma osmolarity of a subject is raised to 320 mOsm/L. This triggers the release of a hormone from the posterior pituitary that increases the reabsorption of water from urine in the collecting ducts. Which of the following is an additional function of this hormone?  

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Antidiuretic hormone (ADH) p. 340, 612

in diabetes insipidus p. 344

hypothalamus synthesis p. 511

kidney effects p. 614

nephron physiology p. 609

pituitary gland and p. 339

SIADH and p. 344

signaling pathways of p. 353

Antidiuretic hormone (ADH) antagonists p. 364

Blood pressure

antidiuretic hormone regulation of p. 340

Diabetes insipidus p. 351

antidiuretic hormone in p. 340

Serum osmolarity

antidiuretic hormone regulation of p. 340

Syndrome of inappropriate antidiuretic hormone secretion p. 351

Vasopressin p. 340, 614

Vasopressin receptors p. 239


Antidiuretic hormone, or ADH, is a peptide hormone that is anti- or against -diuresis which is excessive urine production.

Antidiuretic hormone is also called vasopressin because it causes vasoconstriction - constriction of blood vessels.

So antidiuretic hormone prevents making too much urine, which leads to water retention, and vasoconstriction, and together these two actions help increase the blood pressure.

Now, the brain has two interconnected structures: the hypothalamus and the pituitary gland. These two structures are connected by the pituitary stalk.

The hypothalamus is a part of the brain that contains several nuclei, or clusters of neurons. And two of these nuclei, the paraventricular and supraoptic nuclei, contain neurons that secrete ADH.

When ADH is produced, it travels down the axons of these neurons, and these axons have small dilations called Herring bodies, which is where ADH is stored.

When the body needs more ADH, the stored hormone is released and continues down the axon through the pituitary stalk.

From there it’s released into the posterior pituitary gland which is interstitial tissue near capillary beds, so that the ADH can easily enter the bloodstream.

Let’s say that it's a super sunny day out and you forget to bring water with you. Well first, as you walk around, you’re constantly losing water through sweat as well as water vapor from your mouth and nose as you breathe out - these are insensible water losses. Without drinking water, you can quickly get dehydrated. This causes your plasma osmolarity to increase, because the fluid levels in your blood drop, but the total number of solute particles remains roughly the same.

Now, two things now begin to happen simultaneously. First, a region in the brain called the anterior hypothalamus has a cluster of neurons called supraoptic nuclei, which have osmoreceptors that sense even tiny changes in osmolarity, as small as 1 mOsm/L. These neurons are always sampling the blood that passes by and they have a special channel called aquaporin 4 which allows water to freely enter or exit the cell.


Antidiuretic hormone (ADH), also known as vasopressin, is a hormone that regulates water and electrolytes (e.g. sodium) balance. It does so by increasing water reabsorption into the bloodstream by acting on the kidneys nephrons. ADH is synthesized in the hypothalamus, and released into circulation from the posterior pituitary gland. Its secretion is triggered by states of hypovolemia like hemorrhage, dehydration and thirst.


  1. "Medical Physiology" Elsevier (2016)
  2. "Physiology" Elsevier (2017)
  3. "Human Anatomy & Physiology" Pearson (2018)
  4. "Principles of Anatomy and Physiology" Wiley (2014)
  5. "SIADH Associated With Ciprofloxacin" Annals of Pharmacotherapy (2013)
  6. "The Challenge of Translation in Social Neuroscience: A Review of Oxytocin, Vasopressin, and Affiliative Behavior" Neuron (2010)
  7. "Vasopressin and the regulation of aquaporin-2" Clinical and Experimental Nephrology (2013)

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