What are parathyroid glands?

The parathyroid glands are four tiny structures that are embedded in the rear surface of the thyroid gland. They are responsible for secreting parathyroid hormone ( PTH ). PTH increases the concentration of Ca2+ in the blood. It does this in three ways:

1. PTH causes release of Ca2+ from the huge reservoir in the bones. 99% of the calcium in the body is incorporated in our bones.

2. PTH helps the re-absorption of Ca2+ from the fluid in the tubules in the kidneys.

3. PTH also helps the absorption of Ca2+ from the contents of the intestine.

The single major disease of the parathyroid gland is overactivity of one or more of the parathyroid glands. which make too much of the parathyroid hormone that can cause a serious calcium imbalance. This condition is called hyperparathyroidism. Tumors in the parathyroid glands can cause this condition to occur by elevating the level of parathyroid hormone that causes a rise in the level of Ca2+ in the blood at the expense of calcium stores in the bones.

So much calcium can be withdrawn from the bones that over the long run one may develop osteopenia where the bones become brittle and increase risk of fracture.

Treatment for Hyperparathyroidism would be to remove the hypersecreting abnormal gland(s). In about 90% of situations, only one of the 4 glands has grown as a benign tumor and is the only one that is abnormal and hypersecreting. This condition is called parathyroid adenoma.

In about 10% or less of patients with hyperparathyroidism all 4 glands have grown large (hyperplasia) and secrete too much PTH. This condition is called parathyroid hyperplasia.

How is parathyroid adenoma treated?

The key in treating this condition is identifying which of the four glands has become an adenoma by trying to localized it using a scan called parathyroid sestamibi scan, and also using a sonography. If the abnormal gland can be localized with these techniques, then a minimally invasive surgery can be done to remove the gland.

This surgery would be performed by an ENT-Head and Neck Surgeon and you would then be followed up medically by your endocrinologist or primary care physician who more than likely discovered the hyperparathyroidism in the first place for medical management.

Can one have more than one adenoma?

Yes, however, this condition is rare and occurs in less than 1% of the cases.

How is parathyroid hyperplasia treated?

In this condition typically all hypersecreting glands are removed surgically and then part of one is either re-implanted in a muscle in neck or forearm or part of one is left in place if it is not enlarged.

Imaging for hyperparathyroidism and targeted minimally invasive surgery

Radiologic imaging of choice for primary hyperparathyroidism are parathyroid sestamibi scan and sonography (ultrasound). During parathyroid scanning, an injection of technetium sestamibi is given to the patient. Technetium sestamibi is taken up by both the thyroid and parathyroid glands. However, parathyroid adenomas typically concentrate the sestamibi and hold onto it, while thyroid gland lets it go.

Imaging of the neck is done immediately after the injection and again in one and two hours after the injection. During early images both thyroid and potential parathyroid adenoma light up on images. However in late images normal thyroid lets go (wash out) of sestamibi and only parathyroid adenoma may light up, diagnosing an adenoma and showing on what side and approximate position it is located.

However, certain thryoid nodules can also hold on to sestamibi. So an ultrasound of thyroid is also needed to rule out any thyroid nodule that may cause a false positive sestamibi scan and at the same time to look for an extrathyroid nodule around the same area that sestamibi shows a possible parathyroid adenoma. These late images at 1 and 2 hours post injection are called washout images.

Sestamibi scan is done with SPECT (Single Photon Emission Computed Tomography) and washout images. The latest technology in sestamibi parathyroid scanning utilizes a SPECT-CT fusion to precisely delineate the anatomic location of the adenoma in relation to other anatomic structures in the neck. CT scan has the capacity to show the detailed anatomy. When the SPECT sestamibi scan is superimposed on CT scan the exact location of the adenoma within the neck becomes evident when it is visible on SPECT.