Antidiuretic hormone is produced from the pituitary gland. It is also called vasopressin. When the water level in the blood decreases, more ADH is secreted. It increases the water absorption capacity of the renal tubules. As a result, the volume of urine decreases and the concentration of urine increases. The quantity and number of urine released from the body decreases. On the other hand, when the water level in the blood increases, the amount of ADH secretion decreases. This reduces the water absorption capacity of the renal tubules. As a result, urine volume increases and urine concentration decreases. The quantity and number of urine released from the body increases. Human diabetes insipidus occurs when the ADH production of the pituitary gland decreases.