Which hormone directly affects the permeability of the collecting duct to water?

Which hormone directly affects the permeability of the collecting duct to water?

a. ANP

b. ADH

c. BNP

d. Aldosterone

Answer: b. ADH

In the hypothalamus, there is production of ADH and its release into the posterior pituitary gland. Its major function is to regulate the degree of water being returned to the kidneys by changing the level of absorption of the substance by the collecting duct cells.

For instance, when ADH levels are high; it bonds with the receptors on the collecting duct cells and this leads to the incorporation of the aquaporin channels. These channels enable the emptying of water back into the bloodstream in the collecting duct, thus rendering concentrated urine.

On the other hand, therefore, low levels of ADH mean that free access to water is granted from being reabsorbed in the collecting duct in preparation for urine formation, and as such, we have dilute urine. Ultimately, hormonal regulation of water permeability of the collecting ducts, the physiological requirements in water balance and osmotic homeostasis are taken care of in the body.