Low blood levels of which substance would cause the release of more adh into the blood?

Low levels of water in the blood, causes more release of anti-diuretic hormone (ADH) into the blood. It causes increases in the retention of water in the kidneys, and thus, blood volume is increased. This may be caused by dehydration and leads to less volume of urine. It is released by the hypothalamus and stored in the posterior pituitary. 

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