 Hey everybody, Dr. O. This video we're going to talk about the parathyroid glands and parathyroid hormone. So here we see the back of the larynx and the trachea. You can see there in the front that large bilobed thyroid gland. We're looking at those small blue structures. There's usually two pairs or four parathyroid glands. They're embedded there in the back of the thyroid gland. So then here we see just a functional tissue of the parathyroid gland. The most important cells are called the parathyroid cells or the chief cells. Let's go ahead and look at what parathyroid hormone does. We just finished talking about the thyroid gland and how it produces a hormone called calcitonin. That's important if your blood calcium levels get too high. Parathyroid hormone is much more important, at least much more powerful, and its job is to kick in when blood calcium levels drop and get too low. Let's go ahead and see what happens. So let's go through the list here. Number one, blood calcium concentrations drop. That's going to cause those chief cells of the parathyroid glands to release parathyroid hormone. What's it going to do? The two big things it's going to do, and there's lots of them. The first two I focus on are it's going to stimulate the osteoclasts. These are going to be the cells, these huge multinucleate cells that have digestive enzymes that digest and break down bones. So it's going to stimulate them while inhibiting the osteoblast that would actually build bones. So we'll look at some of the other functions here, too, though. So 3A, the effects of parathyroid hormones, we just said inhibits osteoblasts, stimulates osteoclasts. It's going to break bone down, releasing that calcium into the bloodstream. Then it's going to have an impact on the kidney. It's going to have an impact, actually. Parathyroid hormone is going to tell the kidney tubules to reabsorb more calcium and magnesium rather than passing it into your urine. The other thing that parathyroid hormone is going to do is to tell the kidneys to release calcitriol. Calcitriol is basically, it's the hormone that converts vitamin D3 into its active form. So you're going to have more vitamin D. So those are going to be some more effects of parathyroid hormone. And then the effects on the intestines, it's going to increase the absorption of calcium so you get more calcium coming into your body, whereas calcitonin decreased absorption of the kidneys. So what that's going to do is going to cause your blood calcium levels to come back up, and that's how it should work. But if they get too high, then the opposite's going to happen. Calcitonin's going to get back involved. We already covered calcitonin. It's going to do the opposite. It's going to decrease absorption of calcium at the gut, increase urinary excretion of calcium. It's going to get your osteoblasts. Your bone builders are going to be activated, and it's going to turn off your osteoclasts, the bone breakers, the bone digesters. So the balance between the two should leave you with good blood calcium levels. A lot of this depends on your dietary intake, though. I like to tell people that once you've reached peak bone density, every day that you're not getting enough calcium, vitamin D, vitamin K2, whatever nutrients you want to talk about, every day you're not physically active and stimulating your bones, they're going to get a little bit weaker. But the big one is so maintaining blood calcium levels are very important. You might think well maintaining bones are very important too. But calcium's needed every time a nerve is transmitted. It causes the release of neurotransmitters. It's needed every time a muscle contracts. Your thin and thick filaments can't work without calcium. It's needed for buffering pHs and keeping you from dying from having an acid base disturbance. It's needed for countless things like that. So as far as your body's concerned, keeping strong healthy bones for 30, 40, 60 years from now, that is a luxury. Your body needs to keep the enough calcium in your blood in order to keep you living today, keeping your heart beating and those kind of things. Okay, that is the parathyroid glands and the parathyroid hormone they produce. I hope this helps. Have a wonderful day. Be blessed.