How ADH Helps Regulate Water Reabsorption The kidneys are highly specialized organs that regulate water homeostasis in the human body. They are composed of functional units called the nephrons. Within the nephron, the majority of water homeostasis takes place in the collecting duct, as this component is responsible for water excretion (Sands & Layton 2017). The crucial hormone that is released in the collecting duct and is responsible for stimulating water retention is the antidiuretic hormone (ADH), commonly known as vasopressin (Park & Kwon 2017). The secretion of this hormone is catalyzed by osmolality, which is the concentration of salt (ions) in the blood (Park & Kwon 2017). When ADH is present, the collecting duct of the nephron
