Understanding parathyroid hormone and hypoparathyroidism

Hormones are compounds that travel through the body and act like chemical messengers. Growth, development, mood, appetite, metabolism, sleep, and many other processes are regulated by different hormones. Hormones are produced by specialized cells and tissues in the body (called endocrine cells or tissues) and released into the bloodstream.

Hypoparathyroidism is a medical condition where the body has very low levels of a specific hormone called parathyroid hormone (PTH).

Here are five things to know about PTH and hypoparathyroidism.

PTH is produced in the parathyroid glands

Parathyroid hormone is named for the glands that produced it, called the parathyroid glands. These four pea-sized glands are named for their location, directly behind the thyroid gland, located in the front of the neck (para meaning “alongside” or “beside”).

The most common cause of hypoparathyroidism is injury to the parathyroid glands. Because of their location, damage to these glands can occur during surgery, such as surgery to remove a tumor or thyroid surgery.

Other causes include genetic disorders, autoimmune disease, and low magnesium levels.

PTH regulates blood calcium levels

Calcium is a mineral that the body gets from the foods a person eats (the body cannot produce calcium on its own). Roughly 99 percent of the calcium in the body is stored in bones. The remaining one percent circulates in the blood, where it plays a critical role in the functioning of the cardiovascular system, nervous system, and skeletal muscles. Calcium is constantly being exchanged between the blood and bones to maintain calcium levels.

When PTH levels are low, calcium levels also become low. This can cause tingling, numbness, pain, headaches, fatigue, and brain fog. It can lead to serious complications. Hypoparathyroidism can cause muscle spasms in the airways (making it difficult to breathe), heart problems (arrhythmias, cardiomyopathy, heart failure), kidney problems (kidney stones, chronic kidney disease), and seizures.

PTH maintains calcium with several mechanisms

The cells that make up the parathyroid glands have specialized proteins called calcium-sensing receptors. These proteins act like an on/off switch for PTH production. When blood calcium levels are normal, calcium attaches to the calcium-sensing receptors, and PTH production slows down. When blood calcium levels are low, the switch stays on, and the parathyroid glands produce and release PTH into the bloodstream.

As it circulates in the blood, PTH maintains the calcium levels through several mechanisms:

• It causes bones to release small amounts of calcium into the blood.
• It prevents the kidneys from filtering calcium out of the blood and into urine and promotes the reabsorption of calcium into the bloodstream.
• It stimulates the conversion of vitamin D into its biologically active form, called calcitriol. This active form promotes calcium absorption in the intestines and kidneys.

PTH also balances phosphate levels

Phosphate is a mineral that works alongside calcium. Like calcium, phosphate plays an essential role in the normal functioning of bones, nerves, and muscles. PTH helps control how much phosphate is expelled in urine and how much is absorbed by the digestive system.

The body needs a balance of both calcium and phosphate. As calcium levels drop due to hypoparathyroidism, phosphate levels increase. When calcium and phosphate are not balanced, it can impact bone quality and damage blood vessels.

Synthetic versions of PTH may be used in treatment

Treatment for hypoparathyroidism will depend on the underlying cause. For example, hypoparathyroidism caused by low magnesium will be treated by addressing the underlying magnesium deficiency.

The main treatment for hypoparathyroidism is a combination of calcium supplements and prescription medications containing calcitriol. This requires regular monitoring for calcium levels, phosphorous levels, and kidney function.

Thiazide diuretics, medications that prevent calcium loss through urine, may also be prescribed. A healthcare provider may also recommend following a high-calcium, low phosphate diet.

In some cases, hypoparathyroidism can be treated with parathyroid hormone injections. These injections work by replacing the PTH that is not being made by the body.

A healthcare provider will be your best source of information about your diagnosis, treatment options, potential side effects of different treatment options, and dietary guidelines.