What is ADH? - Definition & Function

What is ADH? - Definition & Function
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  • 0:02 What is ADH?
  • 0:45 The Function of ADH
  • 3:42 Other Factors…
  • 4:51 Lesson Summary
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Lesson Transcript
Instructor: Adrianne Baron

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

Learn what ADH stands for and what it means. We will take a look into the function of ADH in the body as well as factors that can alter its function in the body. There is a short quiz to follow.

What is ADH?

At first glance, you may be thinking that ADH probably stands for some type of a disorder like ADHD or ADD. While the letters are similar, ADH is not a disorder. ADH stands for antidiuretic hormone, which is also known as vasopressin, and it looks like this:

ADH is produced in the hypothalamus and stored in the pituitary gland. It's released from there into the bloodstream, and it affects how the kidneys work by letting them know how much water they need to keep in or get out of the body. You may not know it, but you can actually see it at work pretty easily!

The Function of ADH

Let's say you are a normal, healthy adult who drinks the recommended amount of water on a daily basis. Then you change your routine for a week and drink less water than usual. Around the second or third day of the week, you go to the bathroom to urinate and realize that your urine smells really strong and it's a deeper color yellow than normal. The next day, you notice that the smell is even stronger and the color is even darker. Then you go back to drinking water as you normally do, and the smell and color of your urine becomes less intense, returning to normal. What you've just seen is the result of ADH hard at work.

When you decreased your water intake, this decreased the amount of water in your bloodstream. Blood and other cells in your body need to be surrounded by just the right amount of water, so too little or too much water in the body is dangerous.

Fortunately, we have a built-in alarm system of sorts. When the blood flows past the hypothalamus, which is the detection center of the brain, any imbalance of water in the blood is detected. If there's a problem, the hypothalamus goes to work to correct things by telling the pituitary gland how much ADH to release.

So, going back to the week when you don't drink enough water, here's what happened: the hypothalamus detected potential dehydration and sent a signal to your pituitary gland telling it to increase the amount of ADH being released into your bloodstream. The additional ADH reached your kidneys, telling them to decrease the amount of water to be excreted in your urine and increase the amount put back into your bloodstream. This continued until the hypothalamus detected the normal amount of water in the blood.

In other words:

Decrease in water intake > Increase in ADH > Decrease in urine output

Now let's look at the opposite scenario. You drink too much water, thinking if some is good, more must be better, right? A day or two of this and you'll notice that your urine is looking very clear and has next to no smell at all. It probably doesn't need to be said that you'll have lots of opportunities to notice this.

The hypothalamus will now detect too much water in the blood, which is also dangerous for the cells in your body; dehydration isn't the concern any more, drowning is! So it's going to send a signal to the pituitary gland to decrease the amount of ADH being released. The decrease in ADH will tell the kidneys to excrete more water into your urine and absorb less back into the bloodstream.

This means:

Increase water intake > Decrease ADH > Increase urine output

And…back to normal. When water levels in the blood are optimal, they are considered to be in a state of homeostasis. When homeostasis exists, the hypothalamus tells the pituitary gland to release the normal amount of ADH, telling the kidneys to retain and excrete the right amount of water necessary to retain balance.

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