Anti-diuretic Hormone (ADH)

Antidiuretic hormone (ADH) is a hormone produced by the pituitary gland. It plays a crucial role in maintaining the body’s water balance by controlling the amount of water reabsorbed by the kidneys.

Water reabsorption occurs along the nephron tubules in the kidneys. When the water content of the blood is too low, ADH is released by the pituitary gland, which makes the kidney’s nephron tubules more permeable to water, allowing them to absorb more water.

When the water content of the blood is too high, the pituitary gland stops releasing ADH which makes the nephron tubules less permeable to water. 

ADH in Action

  • Water Loss – When the body loses water (e.g., through sweating), the blood becomes concentrated. The pituitary gland responds by releasing ADH.
  • ADH Effect – ADH makes the kidney tubules more permeable, allowing more water to be reabsorbed back into the blood. This reduces urine production and increases blood water levels.
  • Water Gain – If the body gains too much water (e.g., through drinking), the pituitary gland stops releasing ADH. This leads to less water reabsorption, more urine production, and a return to normal blood water levels.
Blood Plasma ConcentrationProblemADH ReleaseADH Effects
HighToo little waterIncreasesMore water is reabsorbed by nephron tubules
LowToo much waterDecreasesLess water reabsorbed by nephron tubules

The control of water reabsorption by the kidneys’ nephron tubules is an example of negative feedback.

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