Parathyroid Anatomy

Characterized by a small, bean-like shape, the four parathyroid glands are located near the thyroid gland. About 4-8mm in size, these glands are responsible for the production of the parathyroid hormone (PTH), which helps maintain calcium levels in the body (calcium homeostasis). While calcium is essential for normal cell functions, too much or too little can weaken bones and interfere with how the brain and heart function. Excess productive of PTH is what causes hyperparathyroidism.

Appearance of Parathyroid Glands

The parathyroid glands have a smoother surface than thyroid glands. The color is usually tan or light brown, although surrounding fat may obscure the glands’ coloration. Approximately 10 percent of patients are missing one of the arteries shared by the parathyroid glands and the thyroid glands. An artery branch from another thyroid gland still allows blood to be transferred to the affected gland. Positioning of any of the four parathyroid glands may vary slightly in each individual.

Parathyroid Anatomy UCI Head Neck 1 - Parathyroid Anatomy
Parathyroid Anatomy UCI Head Neck 2 - Parathyroid Anatomy

Parathyroid Glands and Calcium Absorption

The main function of the parathyroid glands is to control the release of calcium to bones and increase absorption in the stomach and digestive tract. In addition to promoting healthy bone growth, calcium is essential because it also helps activate vitamin D to further boost calcium absorption. Calcium also plays a role in blood clotting, calcium reabsorption in the renal tubules in the kidneys, and the transmission of messages in nerves.

Potential Problems with Parathyroid Glands

Benign (non-cancerous) tumors called adenomas sometimes develop on the parathyroid glands. These tumors produce excessive amounts of the PTH hormone, which leads to hyperparathyroidism. The majority of cases (about 85 percent) involve a single parathyroid gland tumor. Signs that the parathyroid glands aren’t functioning properly can range from mild symptoms such as tiring easily or general weakness to severe symptoms like fragile bones, excessive urination, loss of appetite, and abdominal pain. Parathyroid glands may also be affected during thyroid surgery since these tissues share the same blood supply.

While anybody can be affected by calcium imbalance due to PTH production problems, the average age of diagnosis is early-to-mid fifties. It is possible for a cancerous tumor to be the cause of hyperparathyroidism, although this is rare. Women tend to have PTH imbalances more than men (3:1 ratio). Hyperparathyroidism is sometimes a secondary condition brought on by another chronic abnormal stimulus, usually kidney failure. Half of all patients who have a kidney transplant have elevated PTH levels for more than a year after their operation.

A referral may be made to an ear, nose, and throat specialist if there is a suspected problem with either the thyroid or parathyroid glands. If symptoms are related to an over-production of PTH, treatment may include monitoring of the condition to see if calcium levels return to normal or surgery to remove the parathyroid glands that have a tumor that’s causing excess calcium production. Certain medications (calcimimetics) may “trick” the parathyroid glands into producing less of the PTH hormone and restore normal calcium levels.

Parathyroid Anatomy UCI Head Neck 3 - Parathyroid Anatomy