Why Is Calcium Monitored After a Thyroidectomy?

During a thyroidectomy, or surgical removal of part or all of the thyroid gland, damage to the parathyroid glands, located on the thyroid, can occur. Your calcium levels can drop below normal as a result of the surgery because the parathyroids regulate calcium levels in your blood. Your doctor should monitor your calcium levels following thyroidectomy.

Surgeons operating on a patient (Image: Keith Brofsky/Photodisc/Getty Images)

Thyroidectomy

A thyroidectomy is an operation performed to remove cancerous growths or other diseased portions of the thyroid gland. Your four parathyroid glands sit immediately behind the thyroid. Despite their close proximity, your parathyroid and thyroid glands have separate functions. A surgeon performing a thyroidectomy usually tries to avoid damage to the parathyroid glands by leaving some thyroid tissue around them intact. However, damage can still sometimes occur.

Hypoparathyroidism

Damage to the parathyroid glands can cause hypoparathyroidism, or underactivity of the glands, and the production of parathyroid hormone (PTH), which maintains normal calcium levels, may be interrupted. If so, your blood calcium will drop. This can have serious consequences. Calcium is an essential mineral for your health. As a matter of fact, your body regulates it more closely than any other mineral. It is necessary to maintain your bones and the proper function of your muscles and nervous system.

PTH and Calcium Levels

Your parathyroid glands have an extensive blood supply that enables them to respond quickly to keep your calcium levels within a narrow range, between about 9 and 10 mg/dL. Studies have shown that PTH levels falling below 10 pg/mL during thryoid surgery is a strong predictor of hypoparathyroidism following the procedure, which can lead to hypocalcemia. PTH levels are not typically monitored during a thyroidectomy.

Hypocalcemia

Abnormally low levels of calcium can cause symptoms like confusion, muscle cramps and tingling. Under normal circumstances, your parathyroids would not allow this to happen. Before your calcium level drops too low, more PTH is released into the blood. This controls calcium levels in two ways. It causes your bones to release calcium and your intestines to absorb more calcium from food. When blood levels return to normal, less PTH is released.

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