The correct answer is Vasopressin.Vasopressin is related to the concentration of urine.It is also called the Antidiuretic hormone secreted by the posterior pituitary gland.It mainly acts on the kidney and stimulates the reabsorption of water by the distal convoluted tubules and thereby reducing the loss of water through urine (Diuresis) so-called antidiuretic hormoneThe reabsorption of water makes the urine more concentrated.Important Points The deficiency of ''Vasopressin'' results in a disease called 'Diabetes insipidus'.Due to a lack of vasopressin, the body cannot retain the required amount of water and it is lost in the urine, so the person feels thirsty all the time.