REGULATION OF WATER IN HUMAN BODY
The maintenance of a correct water balance (the net difference between water gain and water losses) is essential to good health.
It is all the more essential as there is no real water storage in the body: the water we lose needs be replaced, and humans cannot survive more than a few days without water.^1,2
We lose water on a daily basis.

• Through the respiratory tract (by breathing)
• Through the gastro-intestinal tract (faeces)
• Through the skin (perspiration and sweating)
• Through the kidneys (urine excretion)Lifestyle and environmental conditions have a significant impact on an individual’s own level of water loss, but on average, a typical adult loses about 2.6 litres (L) per day.³
  
  Table: Average daily water loss from different organs in adults³
  

  
  Additional water losses via sweat will be induced by physical exercise and/or a hot environment and could contribute to water losses of up to several litres.
  We gain water through fluid and food intake and metabolic water production mainly through food nutrient utilization by the body. Metabolic water production represents 0.3 L per day, on average, and water from foods can vary greatly according to dietary habits. Our remaining requirement needs to be provided by fluids. The endocrine system mediates many of the physiological responses to the homeostatic and acclimation demands of salt and water transport. Many of the hormones involved in the control of salt and water transport are common to all vertebrates, although their precise function and target tissues have changed during evolution. Arginine vasopressin (vasotocin), angiotensin II, natriuretic peptides, vasoactive intestinal peptide, urotensin II, insulin and non-genomic actions of corticosteroids are involved in acute (minutes and hours) alterations in ion and water transport. This rapid alteration in transport is primarily the result changes in behavior, blood flow to osmoregulatory organs, and membrane insertion or activation (e.g., phosphorylation) of existing transport proteins, ion and water channels, contransporters and pumps. Corticosteroids (through genomic actions), prolactin, growth hormone, and insulin-like growth factor I primarily control long-term (several hours to days) changes in transport capacity that are the result of synthesis of new transport proteins, cell proliferation, and differentiation. In addition to the important task of establishing broad evolutionary patterns in hormones involved in ion regulation, comparative endocrinology can determine species and population level differences in signaling pathways that may be critical for adaptation to extreme or rapidly changing environment
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• links;www.bio.umass.edu/biology/mccormick/pdf/GCE
• https://quizlet.com/11975873/hormonal-control-of-water-and-sodium