What the parathyroid hormone does is it increases the concentration of our calcium inside our blood. So this type of hormone is responsible for maintaining and regulating the concentration of calcium inside our blood. Now, the release or inhibition of the parathyroid hormone is controlled by the concentration of calcium inside of our blood. Now, when the blood calcium level drops, when it's relatively low, the parathyroid gland releases the parathyroid hormone. And this basically increases the concentration of calcium inside our blood as a result of three different things. So it basically does three important things.