This hormone helps the kidneys control the amount of water your body loses through the urine. SIADH causes the body to retain too much water. ADH is a substance produced naturally in an area of the brain called the hypothalamus. It is then released by the pituitary gland at the base of the brain.

What stimulates ADH secretion?

The most important variable regulating antidiuretic hormone secretion is plasma osmolarity, or the concentration of solutes in blood. Osmolarity is sensed in the hypothalamus by neurons known as an osmoreceptors, and those neurons, in turn, stimulate secretion from the neurons that produce antidiuretic hormone.

Why does ADH cause vasoconstriction?

ADH decreases the volume of urine by increasing the reabsorption of water in the kidneys. ADH causes contraction of vascular smooth muscles, constriction of arterioles, and peripheral vasoconstriction. This manifests at the skin as palor and brings about vasodilation of the coronary and cerebral arteries (Fig. 3.5).