Comment upon the hormonal regulation of selective reabsorption.

(N/A) The hormonal regulation of selective reabsorption in the kidneys is primarily controlled by the $Renin-Angiotensin-Aldosterone$ $System$ $(RAAS)$ and $Antidiuretic$ $Hormone$ ($ADH$ or $Vasopressin$).
$1$. $RAAS$: When blood pressure or glomerular blood flow decreases,the $Juxtaglomerular$ $(JG)$ cells release $Renin$. $Renin$ converts $Angiotensinogen$ in the blood to $Angiotensin-I$ and further to $Angiotensin-II$. $Angiotensin-II$ is a powerful vasoconstrictor that increases glomerular blood pressure and stimulates the adrenal cortex to release $Aldosterone$. $Aldosterone$ causes the reabsorption of $Na^+$ and water from the distal convoluted tubule $(DCT)$ and collecting duct,thereby increasing blood volume and pressure.
$2$. $ADH$: An increase in body fluid volume or osmolarity triggers the hypothalamus to release $ADH$ from the neurohypophysis. $ADH$ facilitates water reabsorption from the later parts of the tubule (collecting duct),preventing diuresis and maintaining water balance.