Function and Diseases of the Parathyroid Glands

Understanding Normal and Abnormal Parathyroid Glands

The location of the parathyroid glands (right).
The location of the parathyroid glands (right). Stocktrek Images/Getty Images

The parathyroid glands are small glands, about the size of a small bean, located near the thyroid gland in the neck. These glands play an essential role in the regulation of calcium in the body. While diseases can affect this gland, cancer rarely does.

Is The Parathyroid Gland Similar to the Thyroid Gland?

No. While they share similar names and are located closely to one another, the thyroid and parathyroid gland are not dependent on each other to function.

What is the Function of the Parathyroid Glands?

Parathyroid glands are responsible for regulating calcium, an essential element in our body for nerve and muscle function. Calcium is regulated through a hormone called the parathyroid hormone, or PTH.

When calcium levels in the bloodstream become low, PTH stimulates the release of calcium from bone. It also stimulates the reabsorption of calcium in the kidneys — which means less calcium is excreted in the urine. In addition, PTH converts the inactive form of vitamin D to the active form of vitamin D. This active form of vitamin D increases the absorption of calcium in the gut, which further increases calcium levels in the bloodstream.

When calcium levels are high in the bloodstream, the parathyroid glands lower its PTH production. This prevents calcium from being leeched from the bones and allows for more calcium to be excreted in the urine.

What is Hyperparathyroidism?

Like other organs and glands in the body, the parathyroid is vulnerable to disease.

One common disease that affects the parathyroid gland is primary hyperparathyroidism, which is characterized by a hyperfunctioning parathyroid gland and an overproduction of the PTH hormone. Primary hyperparathyroidism is commonly due to a benign tumor (non-cancerous) in one of the parathyroid glands or overgrowth of the gland, called parathyroid hyperplasia.

Rarely, a cancer of the parathyroid gland is the cause.

Secondary hyperparathyroidism may occur as a result of vitamin D deficiency. This is because vitamin D deficiency causes a drop in calcium levels in the body, which triggers the parathyroid gland to release PTH. Kidney disease can also cause hyperparathyroidism because the inactive form of vitamin D is not properly converted to active vitamin D.

Certain cancers, like lung cancer, may release a hormone that is related to and mimics the parathyroid hormone, causing symptoms of hyperparathyroidism like muscle aches, fatigue, depression, and constipation.

What is Hypoparathyroidism?

Hypoparathyroidism, in which the parathyroid glands do not function properly, may also occur — although this is less common, since most people have 4 parathyroid glands, so there is usually a back-up. The most common cause of hypoparathyroidism is damage to the glands during surgery of the neck, like during thyroid surgery.

Other rare causes include genetic diseases of newborns, autoimmune diseases, a liver disease called Wilson's disease, iron overload, or a cancer that spreads or metastasizes to the parathyroid gland.

What Does This Mean for Me?

If your doctor suspects you have a problem with your parathyroid gland or calcium levels, you will be referred to an endocrinologist. The good news is the common causes of parathyroid disease, like primary hyperparathyroidism, can generally be treated effectively.

Sources:

Mills, SE. Histology For Pathologists, Third Edition. Philadelphia: Lippincott Williams & Wilkins, 2007.

Nussey S. Endocrinology: An Integrated Approach. Chapter 5: The parathyroid glands and vitamin D

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