Anti-diuretic hormone (ADH) and
Aldosterone work together to regulate water and electrolytes in the blood.
Anti-diuretic
hormone (ADH)
- a hormone that is produced by the hypothalamus and released by the posterior pituitary into the blood stream.
- It is also a hormone that helps to control blood pressure by acting on the kidneys and the blood vessels.
- Its most important role is to conserve the fluid volume of your body by reducing the amount of water passed out in the urine. It does this by allowing water in the urine to be taken back into the body in a specific area of the kidney. Thus, more water returns to the bloodstream, urine concentration rises and water loss is reduced. Higher concentrations of anti-diuretic hormone cause blood vessels to constrict (become narrower) and this increases blood pressure.
- Secretion of anti-diuretic hormone also occurs if the concentration of salts in the bloodstream increases.
ADH plays a
role in lowering osmolarity (reducing sodium concentration) by increasing water
reabsorption in the kidneys, thus helping to dilute bodily fluids. To prevent
osmolarity from decreasing below normal, the kidneys also have a regulated mechanism
for reabsorbing sodium in the distal nephron. This mechanism is controlled by aldosterone,
a steroid hormone produced by the adrenal cortex.
Aldosterone is released from the adrenal cortex in response to angiotensin I & II and targets the kidney tubules to conserve Na+ ions and H2O while allowing excretion of K+ ions into the urine. Water retention increases blood volume and therefore blood pressure.
Aldosterone also causes the kidneys to excrete potassium. The increased sodium causes water to be retained, thus increasing blood volume and blood pressure.
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