Parathyroid localization for hyperparathyroidism

Hyperparathyroidism is often suspected after an abnormal calcium blood test.  Calcium levels are controlled by parathyroid hormone, which is produced by the parathyroid glands. When the parathyroid glands produce too much parathyroid hormone, calcium blood test results are elevated. When the parathyroid glands produce too little parathyroid hormone, calcium blood test results are low. Both high and low calcium levels cause a multitude of symptoms and problems, some of which are life threatening.

When a patient’s calcium levels are high, the doctor will order a parathyroid hormone test. If the parathyroid hormone levels are elevated, the diagnosis is hyperparathyroidism. The treatment for hyperparathyroidism is removal of the abnormal parathyroid gland or glands.

Most people have 4 parathyroid glands (some people are born with more or fewer glands). Hyperparathyroidism is most commonly caused by a benign tumor of one parathyroid gland (called a parathyroid adenoma). In some other people, 2 or more of the parathyroid glands grow too large, causing hyperparathyroidism. One way to determine how many glands are affected is parathyroid localization scanning.

A sestamibi scan is a radiologic image that can show the location of abnormal parathyroid glands. For this test a very small amount of a safe radioactive substance is injected into a vein of the patient. This substance is absorbed by the abnormal parathyroid gland or glands. X-ray images are then taken, showing the location of abnormal glands. 

Another test used to localize parathyroid glands is neck ultrasound. An ultrasound probe uses sound waves to create images of the tissues in the neck and can often identify enlarged parathyroid glands. Frequently both the sestabmibi scan and neck ultrasound are performed before surgery for localization of the abnormal gland or glands.

These tests are not successful in every patient. In some patients the scanning is negative (no glands appear on the x-ray image or ultrasound). In some patients not all abnormal glands can be identified on the images. It is therefore still important for the surgeon to either examine all of the parathyroid glands during surgery or to perform a parathyroid hormone test following removal of the suspected gland to ensure that the parathyroid hormone levels return to normal. The doctor will continue to monitor patients with a calcium blood test and parathyroid hormone test at follow-up visits.