Hormones are chemical compounds that, when released by the endocrine glands into the blood or nervous system of living beings, exert modulating effects on the functions of other cells and body structures.

One of the most relevant and well-known human hormones is vasopressin or antidiuretic hormone, which is essential for fluid retention or stress response, among other phenomena. In this article we will analyse the properties and functions of vasopressin .

What is vasopressin?

Vasopressin is also known as “argipressin”, “vasopressin arginine” and “antidiuretic hormone” . As the latter name suggests, this hormone has functions related to the reabsorption of water molecules through the kidneys and the decrease in the amount of urine accumulated in the body.

It is an oligopeptide, i.e. a molecule composed by the union of a small number of amino acids, specifically 9. By contrast, polypeptides are groups of between 10 and 100 amino acids, while “proteins” refers to groups of more than 100 such molecules.

Specifically, vasopressin contains an amino group (-NH2), cysteine (Cys), tyrosine (Tyr), phenylalanine (Phe), glutamine (Gln), asparagine (Asn), proline (Pro), arginine (Arg) and a carboxyl group (-COOH).

Vasopressin is secreted by the neuro-pituitary , the posterior lobe of the pituitary gland, in response to changes in osmotic concentration and blood volume. Although most of the vasopressin we produce is released into the bloodstream, its effects on the brain also explain some of its functions.

Other pituitary hormones

The pituitary gland is one of the major endocrine glands . It serves as an intermediary between the hypothalamus, which initiates the secretion of hormones, and the rest of the endocrine system by sending biochemical signals.

This structure is composed of two lobes: the anterior or adeno-pituitary and the posterior or neuro-pituitary. While the posterior pituitary stores the hormones vasopressin and oxytocin (related to motherhood and orgasm), the adenopituitary secretes thyrotropin-releasing hormones, ACTH, gonadotropins, and growth hormone.

Functions of this hormone

The main functions of vasopressin are associated with its ability to regulate the activity of the kidneys; however, this hormone also has effects on other systems in the body, including the cardiovascular and central nervous systems.

1. Fluid retention and reabsorption

Vasopressin increases the permeability of the cells of the kidneys, increasing the amount of water they absorb; this function is called “antidiuresis” . This process also involves an increase in the concentration of urine due to the reduced availability of fluid in the excretory system.

On the other hand, the antidiuretic hormone also reabsorbs urea, the main chemical compound in urine, which is made up of waste products from the body. This prevents excessive frequency of urination.

2. Maintenance of homeostatic balance

Homeostasis (self-regulation of the internal environment of organisms) depends on a large number of factors; among these is the activity of vasopressin. If the homeostatic mechanisms fail, problems such as dehydration and acidosis can occur.

This hormone helps maintain the electrolyte balance of the bloodstream by retaining and reabsorbing adequate amounts of water, glucose and sodium , among other chemicals relevant to the functioning of the body.

3. Increased blood pressure

Another major effect of vasopressin is an increase in blood pressure. This function occurs as a result of the vasoconstrictive properties of this hormone, which have a moderate intensity. The vasopressin-enhancing role on stress associated hormones and neurotransmitters is also important in explaining this effect.

4. Modulation of the stress response

Although scientific research has not yet fully confirmed this, there is strong evidence that vasopressin has a modulating effect on the body’s response to stressful (or anxiety-inducing) situations.

Antidiuretic hormone regulates the release of ACTH, also called “adrenocorticotropic hormone-releasing hormone. This compound promotes the secretion of corticosteroids such as aldosterone and cortisol , mainly associated with vasoconstriction and the stress response, by the adrenal gland.

5. Reduction of pain sensation

In recent years, the involvement of vasopressin in the modulation of pain sensations has begun to be studied. It is believed that this hormone could act as an analgesic ; this would imply that, when released under certain conditions, vasopressin would have reinforcing effects because of the positive sensations associated with its secretion.

6. Forming sexual and social bonds

Studies with rodents suggest that the release of vasopressin also acts as a enhancer of social bonds, especially those of couples . In humans these effects have been found mainly in males and are related to the direct release of antidiuretic hormone into the reward circuits of the central nervous system.