Parathyroid Hormone: What It Does, How It Affects Your Bones and Blood

When your body needs more parathyroid hormone, a key regulator of calcium in the blood produced by the parathyroid glands. Also known as PTH, it’s the main reason your bones release calcium into your bloodstream when levels drop too low. You might never think about it—until your calcium levels go haywire, your bones start aching, or you feel constantly tired. This tiny hormone, made by four small glands behind your thyroid, is silently keeping your muscles, nerves, and heart working right.

It doesn’t work alone. calcium levels, the amount of this mineral circulating in your blood, directly controlled by parathyroid hormone are the main thing PTH watches. If calcium drops, PTH jumps in—pulling calcium from your bones, telling your kidneys to hold onto it instead of peeing it out, and activating vitamin D so your gut can absorb more from food. But when PTH is too high, your bones weaken. When it’s too low, your muscles cramp and your nerves misfire. That’s why hyperparathyroidism, a condition where the parathyroid glands make too much hormone, often leading to high calcium and bone loss is so dangerous, and why hypoparathyroidism, the opposite—too little hormone—can cause seizures and tingling is just as serious.

Most people don’t know their PTH levels until something goes wrong—a broken bone from minor stress, kidney stones, or abnormal blood tests. But understanding how this hormone links to your bones, kidneys, and gut gives you real power. You can spot early signs, ask the right questions, and avoid treatments that ignore the root cause. The posts below cover what happens when PTH goes off track, how it interacts with medications like bisphosphonates and vitamin D, why some drugs mess with calcium balance, and what to do if you’re dealing with chronic low calcium or unexplained bone pain. This isn’t theory. It’s what real patients and doctors deal with every day.