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

When your body needs more calcium, it turns to the parathyroid hormone, a key regulator of calcium and phosphate levels in the blood, produced by the four small parathyroid glands behind the thyroid. Also known as PTH, it’s the main reason your bones don’t weaken and your nerves and muscles keep firing properly. Without it, your blood calcium would drop dangerously low—leading to muscle cramps, seizures, or heart rhythm problems.

Too much parathyroid hormone, often caused by an overactive gland, leading to high calcium levels and bone loss is called hyperparathyroidism. It’s not rare—about 1 in 1,000 people get it, mostly women over 50. Symptoms? Fatigue, kidney stones, bone pain, even memory issues. On the flip side, too little parathyroid hormone, called hypoparathyroidism, often follows thyroid surgery and causes low calcium, tingling, and spasms. Both conditions need real medical attention, not just supplements.

It’s not just about calcium. parathyroid hormone, interacts directly with vitamin D and kidneys to manage phosphate. That’s why people with kidney disease often have messed-up PTH levels—it’s not a standalone problem. And here’s the thing: if your doctor checks your calcium and finds it high, they’ll almost always test your PTH next. It’s the first clue to whether the problem is in your glands or something else.

Most people never hear about PTH until they get a blood test that shows something’s off. But if you’ve had thyroid surgery, suffer from chronic kidney disease, or keep getting kidney stones, you’re in a group that should know what this hormone does. It’s not a buzzword—it’s a critical player in your daily health.

The posts below cover real situations where parathyroid hormone plays a role—whether it’s how certain drugs affect calcium balance, why bone health declines with age, or how medication changes can trigger hidden hormonal shifts. You’ll find practical advice on spotting warning signs, understanding lab results, and what to ask your doctor if your PTH is out of range. No fluff. Just what matters when your body’s calcium system is out of sync.