Antidiuretic hormone (ADH), also known as vasopressin, is a hormone produced in the hypothalamus and secreted by the posterior pituitary gland. One of the primary functions of ADH is to regulate water balance in the body.
When the body is dehydrated, ADH secretion increases, causing the kidneys to reabsorb more water from the urine and reduce urine output. Conversely, when the body is overhydrated, ADH secretion decreases, causing the kidneys to excrete more water and increase urine output.
Therefore, the correct answer is C) Decreases, as ADH decreases urine output by increasing water reabsorption in the kidneys.