The antidiuretic hormone is secreted by the hypophysis (also known as pituitary) and it acts in the nephron tubules increasing the resorption of water. When the body needs to retain water, for example, in cases of blood loss and abrupt blood pressure lowering or in cases of abnormally high blood osmolarity, there is stimulus for ADH secretion.
When the body has an excess of water, as in cases of excessive ingestion or in abnormally low blood osmolarity, the secretion of ADH is blocked and the diuresis increases. ADH is also known as vasopressin since it increases the blood volume and thus heightens the blood pressure.
