ADH Vs Aldosterone

Basic learners of Biology and the concept of the urinary system may somehow have difficulty in separating the roles of ADH and aldosterone. Fortunately for those who have taken advanced courses involving these concepts, the two terms are just like their everyday word.

ADH and aldosterone are two of the most important hormones needed in the regulation of certain body processes that maintain systemic balance. When the overall blood pressure (BP) goes down, the body will automatically counter it by starting a systemic change to increase the BP. Also when the person is severely dehydrated, the body has no other option but to limit urine output and conserve more water for the body cells to use. These processes can be carried out by these two hormones.

ADH is completely known as the antidiuretic hormone. It is also identified as AVP or arginine vasopressin or simply vasopressin. Basically, the difference between the two is regarding the mechanism of action. Although both hormones have the same ultimate goal of water preservation or retention, they have different ways of attaining such. ADH does this by regulating the rate or amount of water reabsorption at the distant tubules of the kidney’s nephrons. It is also said that ADH has the ability to reabsorb urea which, in turn, reabsorbs water through osmosis (movement of water from an area of lower concentration to an area of higher concentration).

On the other hand, aldosterone conserves water in a more indirect manner. It starts off with the reabsorption of sodium. This action will lead to conserving water because water will immediately follow to where the salt is. Aldosterone, like ADH also acts on the distant tubules, but also at the kidney’s collecting ducts.

Water retention with the aid of aldosterone is more complex because it has to undergo the Sodium-Potassium exchange channels. In this set-up, potassium is excreted while sodium is retained.

The places where these two hormones are synthesized also differ. ADH comes from the hypothalamus but is released by the posterior pituitary gland. Aldosterone, like other steroidal hormones like cortisol, comes from the adrenal cortex (the outer layer of the adrenal gland). This hormone also plays a vital role in the renin-angiotensin mechanism ‘“ a very important BP regulating system.

1. ADH is synthesized in the hypothalamus while aldosterone is made in the adrenal cortex.

2. ADH conserves water directly through its reabsorption while aldosterone conserves water indirectly through the reabsorption of sodium.

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