why is vasopressin known as antidiuretic hormone

The major function of vasopressin is to help control the body's water balance by determining how much water is excreted in urine. Normally, when a person's fluid intake is low or when a lot of fluid is lost (for example, through sweating), the pituitary gland releases more ADH into the bloodstream. High levels of this hormone direct the kidneys to reabsorb more water and to make less urine. When fluid intake is adequate, the pituitary gland releases less ADH. Lower levels of this hormone cause the kidneys to reabsorb less water and to make more urine. So, basically its function is to reabsorb more water and control the amount of water excreted as urine and a diuretic is any substance that promotes the production of urine. That is why, it is known as antiduretic hormone.

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