The antidiuretic hormone (ADH) is one of the major hormones controlling fluid balance by inhibiting diuresis or urine output. ADH is secreted by the posterior pituitary gland. For example, when a person is dehydrated, the level of ADH secretion increases so that more water is reabsorbed from the urine and returned to the blood. Conversely, a diuretic such as alcohol inhibits the release of ADH and thus increases urinary output.