What is the meaning of Antidiuretic Hormone (ADH)?

From the Guidelines

The mean antidiuretic hormone (ADH) level is not explicitly stated in the provided evidence, but it is known that ADH plays a crucial role in regulating water retention in the body, and its imbalance can lead to conditions such as the syndrome of inappropriate antidiuretic hormone secretion (SIADH). In patients with lung cancer, approximately 10% to 45% of small cell lung cancer (SCLC) and 1% of other lung cancer cases produce arginine vasopressin (ie, antidiuretic hormone [ADH]), but only 1% to 5% of patients with lung cancer have symptomatic SIADH 1. The diagnosis of SIADH is based on the presence of euvolemic hypoosmolar hyponatremia, characterized by low serum osmolality and inappropriately high urine osmolality in the absence of diuretic treatment, adrenal insufficiency, heart failure, cirrhosis, and hypothyroidism 1. Some key laboratory findings in SIADH include urine osmolality of > 300 mosm/kg, urinary sodium level of > 40 mEq/L, serum osmolality of < 275 mosm/kg, and serum uric acid concentration of < 4 mg/dL 1. The management of SIADH is based on expert opinion, and recommended treatment includes free water restriction, hypertonic 3% saline IV, and the use of demeclocycline, lithium, and vasopressin 2 receptor antagonists (conivaptan, lixivaptan, tolvaptan, and satavaptan) to correct hyponatremia 1. It is essential to note that the treatment of hyponatremia should be started when serum sodium is lower than 130 mmol/L, although there is no good evidence as to what is the level of serum sodium in which treatment should be started 1. In recent years, the pharmacological approach to treatment of hypervolemic hyponatremia has made a step forward with the discovery of vaptans, drugs that are active orally and cause a selective blockade of the V2-receptors of AVP in the principal cells of the collecting ducts 1. Tolvaptan has been recently approved in the USA for the management of severe hypervolemic hyponatremia associated with cirrhosis, ascites, heart failure, and the SIADH, and its treatment is started with 15 mg/day and titrated progressively to 30 and 60 mg/day, if needed, according to changes in serum sodium concentration 1. The use of vaptans has been shown to be effective in improving serum sodium concentration in conditions associated with high vasopressin levels, such as SIADH, heart failure, or cirrhosis, and its administration is associated with an increased urine volume and solute-free water excretion and improvement of the low serum sodium levels in 45–82% of patients 1. However, the treatment with vaptans should always be started in the hospital with close clinical monitoring and assessment of serum sodium levels, to avoid increases of serum sodium of more than 8–10 mmol/L/day, and should not be given to patients in an altered mental state who cannot drink appropriate amounts of fluid because of the risk of dehydration and hypernatremia 1.

From the FDA Drug Label

Desmopressin acetate is a replacement hormone for antidiuretic hormone in the treatment of central diabetes insipidus The antidiuretic effects of desmopressin acetate are mediated by stimulation of vasopressin 2 (V2) receptors, thereby increasing water re-absorption in the kidney, and hence reducing urine production

The antidiuretic hormone is replaced by desmopressin acetate in the treatment of central diabetes insipidus, and it works by stimulating vasopressin 2 (V2) receptors to increase water re-absorption in the kidney, reducing urine production 2.

From the Research

Anti-Diuretic Hormone (ADH) Overview

• ADH, also known as vasopressin, is a hormone that plays a crucial role in regulating water balance in the body 3.
• It helps to control the amount of water reabsorbed by the kidneys, which in turn affects the concentration of the urine and the overall fluid balance in the body.

Disorders of Water Metabolism

• Diabetes insipidus (DI) is a disorder characterized by the inability to regulate water balance, resulting in excessive thirst and urination 4, 5.
• The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is another disorder that affects water balance, causing the body to retain too much water and leading to hyponatremia (low sodium levels) 6, 4.
• Both DI and SIADH can have significant consequences, including hypernatremia (high sodium levels), hyponatremia, and volume depletion, which can lead to worse outcomes and longer intensive care stays 6.

Regulation of ADH

• ADH is secreted by the hypothalamus and stored in the posterior pituitary gland 3.
• The release of ADH is regulated by the osmolality of the blood, with high osmolality stimulating the release of ADH and low osmolality inhibiting its release 4.
• ADH then acts on the kidneys to increase water reabsorption, which helps to concentrate the urine and reduce water loss from the body.

Clinical Significance of ADH

• ADH plays a critical role in maintaining fluid balance and electrolyte homeostasis in the body 3.
• Dysregulation of ADH can lead to various disorders, including DI and SIADH, which can have significant clinical consequences 6, 4, 5.
• Understanding the physiology and regulation of ADH is essential for the diagnosis and management of these disorders.