Final answer:
The hormone that stimulates water reabsorption in the kidneys and induces thirst is Antidiuretic Hormone (ADH), which acts by increasing water permeability in the kidneys' collecting ducts.
Step-by-step explanation:
The hormone that promotes water reabsorption at the kidneys and stimulates thirst is Antidiuretic Hormone (ADH). ADH, also known as vasopressin, is a 9-amino acid peptide released by the posterior pituitary gland. It makes the collecting ducts in the kidneys permeable to water, which allows water molecules to be reabsorbed from the urine back into the bloodstream, reducing urine volume and maintaining plasma osmolarity and blood pressure. ADH achieves this by stimulating the insertion of aquaporin water channels into the cell membranes of the principal cells in the collecting ducts, facilitating the movement of water by osmosis.