Physiology of Dehydration and Overhydration

When the body is in a state of dehydration, many substrates and neurotransmittersare influenced by circulating vasopressin(antidiuretic hormone) and angiotensin II (1,2).

Dehydration can increase levels of cortisol (3). Interestingly, even a decrease in cell volume caused by hypohydration promotes insulin resistance(4,5,6).

Conditions dehydrating insulin target tissues such as hyperosmolarity or amino acid deprivation are associated with insulin resistance; blockage of the cell volume response to insulin may be the common denominator in dehydration-induced insulin resistance (4).

As a consequence of dehydration, the blood–brain barrier permeability is altered by serotonergic and dopaminergic systems, potentially causing central nervous system dysfunction if dehydration is prolonged (7).  

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