Difference Between ADH and Aldosterone

Main Difference – ADH vs Aldosterone

ADH (anti-diuretic hormone) and aldosterone are two types of hormones that increase the water reabsorption in the nephron. ADH is synthesized in the hypothalamus and is stored in and secreted by the posterior pituitary gland. It is also known as vasopressin. Aldosterone is synthesized and secreted by the adrenal cortex. Both hormones are secreted under low blood pressure conditions in the body. Both hormones also act on the distal convoluted tubules (DCT) and collecting tubules of the nephron. The main difference between ADH and aldosterone is that ADH makes the tubules more permeable to water whereas aldosterone makes the tubules more permeable to sodium ions, increasing the water reabsorption by creating an osmotic pressure.

Key Areas Covered

1. What is ADH
– Definition, Secretion, Mechanism of Action
2. What is Aldosterone
– Definition, Secretion, Mechanism of Action
3. What are the Similarities Between ADH and Aldosterone
– Outline of Common Features
4. What is the Difference Between ADH and Aldosterone
– Comparison of Key Differences

Key Terms: ADH (anti-diuretic hormone), Aldosterone, Nephron, Osmolarity, Reabsorption, Renin-Angiotensin-Aldosterone System, Sodium Ions, Vasopressin

What is ADH

ADH refers to a peptide hormone secreted by the pituitary gland, preventing the production of dilute urine. ADH is synthesized in the hypothalamus and it is stored and secreted by the posterior pituitary gland. The main role of ADH is to maintain the fluid balance of the body by controlling the amount of water passed through urine. Thus, ADH produces concentrated urea (diuresis). The role of ADH is shown in figure 1.

Figure 1: Role of ADH

The osmolarity of the blood is monitored by the osmoreceptors in the hypothalamus. These osmoreceptors stimulate the release of ADH from the pituitary gland in response to decreased osmolarities of the blood. Generally, collecting tubules of the nephron are impermeable to water. But, ADH stimulates aquaporins in the membrane of the collecting tubules. Aquaporins are a type of channel proteins that transport solute-free water back to the bloodstream through the tubular cell wall. This may decrease the osmolarity of the blood plasma while increasing the osmolarity of the urine. The release of ADH is stimulated by the decreased blood pressure and volume. ADH acts on the arterioles to increase the blood pressure through vasoconstriction as well. Nausea and vomiting are other two factors that stimulate the release of ADH hormone.

What is Aldosterone

Aldosterone refers to a corticosteroid hormone that stimulates the absorption of sodium by the nephron to regulate water and salt balance. Since it regulates water and salt balance, aldosterone is considered as a type of mineralocorticoid. Aldosterone is synthesized and secreted by the adrenal cortex. The main function of aldosterone is to increase the levels of sodium ions secreted into the bloodstream from the urine. The effect of ADH and aldosterone in the nephron is shown in figure 2.

Figure 2: Effect of ADH and Aldosterone

The action of aldosterone is closely-related with the two hormones known as renin and angiotensin that collectively form the renin-angiotensin-aldosterone system. The activation of the renin-angiotensin-aldosterone system is stimulated by the decreased blood pressure, which reduces blood flow to the kidney. Renin is the hormone responsible for the release of angiotensin, which, in turn, releases aldosterone. The increased concentration of sodium ions in the blood decreases the osmolarity of the blood. The passive reabsorption of water from the kidney tubules may increase in response to the decreased osmolarity of the blood.

Similarities Between ADH and Aldosterone

ADH and aldosterone are two types of hormones that increase the water reabsorption from the nephron.
Both ADH and aldosterone work on the distal convoluted tubules and collecting tubules of the nephron.
Both ADH and aldosterone are secreted under low blood pressure.
The action of both ADH and aldosterone increase the blood pressure while producing concentrated urine.
The levels of ADH and aldosterone in the blood are regulated by negative-feedback loops.

Definition

ADH: ADH (anti-diuretic hormone) is a peptide hormone secreted by the pituitary gland, preventing the production of dilute urine.

Aldosterone: Aldosterone is a corticosteroid hormone that stimulates the absorption of sodium by the nephron to regulate water and salt balance.

Type of Hormone

ADH: ADH is a peptide hormone.

Aldosterone: Aldosterone is a steroid hormone.

Secretion

ADH: ADH is synthesized in the hypothalamus and secreted by the posterior pituitary gland.

Aldosterone: Aldosterone is synthesized and secreted by the adrenal cortex.

Role

ADH: ADH makes the DCT and collecting tubules more permeable to water.

Aldosterone: Aldosterone makes the DCT and collecting tubules more permeable to sodium ions.

Significance

ADH: ADH directly increases the water reabsorption from the tubules.

Aldosterone: Aldosterone increases the water reabsorption by creating an osmotic pressure.

Blood Vessels

ADH: ADH increases the blood pressure through vasoconstriction.

Aldosterone: Aldosterone has no effect on the blood vessels.

Release

ADH: ADH is released in response to hypertonicity of the blood.

Aldosterone: Aldosterone is released in response to the increased plasma angiotensin III, serum potassium concentrations, stimulation of the stretch receptors in the atria, etc.

Conclusion

ADH and aldosterone are two types of hormones that increase the water reabsorption of nephrons. Both ADH and aldosterone act on the DCT and collecting tubules of the nephron. ADH is a peptide hormone that directly increases the permeability of water. However, aldosterone is a steroid hormone that increases the water reabsorption by increasing the osmotic pressure of the nearest blood vessels. Therefore, the main difference between ADH and aldosterone is their mechanism of action.

Reference:

1. “Antidiuretic Hormone”, Available here.
2. “Aldosterone.” Hormone Health Network, Available here.

Image Courtesy:

1. “ADH3” By Rodrigo H. Castilhos – Own work, Public Domain) via Commons Wikimedia
2. “Kidney nephron molar transport diagram” By Nephron-urine.svg: M•Komorniczak -talk-, polish wikipedist.Kidney_nephron_molar_transport_diagram.png: *Nephron-urine.svg: M•Komorniczak -talk-, polish wikipedist.derivative work: Juvo415 (talk)derivative work: Mcstrother (talk) – Nephron-urine.svgKidney_nephron_molar_transport_diagram.png (CC BY-SA 3.0) via Commons Wikimedia