Parathyroid Glands

The parathyroid glands are endocrine ("ductless") glands that secrete parathyroid hormone, which is important for the regulation of calcium levels.  The parathyroid glands are located on each side of the neck along the thyroid gland.  Usually, there are two glands on each side of the neck.  The number of glands and their locations are variable.  The total number can vary from 3 to 8 glands.  There locations can vary from anywhere in the central compartment of the neck to the upper chest (called the mediastinum).  

These glands have a rich blood supply which they share with the thyroid gland.  These parathyroid glands are also closely related to the recurrent (or inferior) laryngeal nerve.  [For more information about the thyroid gland and its anatomy, please look at our thyroid and thyroidectomy pages.]

The regulation of calcium is an extremely complex process.  This process involves parathyroid hormone, calcitonin, vitamin D, calcium, and other hormones and proteins.  The explanation that follows is grossly simplified and is provided to give an overview to our patients that are referred for parathyroidectomy.

The parathyroid glands secrete parathyroid hormone in response to low calcium levels.  This hormone mobilizes calcium from sources within the body, such as bone, to increase the level of calcium in the bloodstream.  C-cells secrete calcitonin in response to high levels of calcium.  The action of this hormone is to lower calcium levels and replace calcium back into bone.

Calcium levels are generally checked as part of a complete physical examination and are included in the most commonly performed metabolic profile blood tests. Abnormally high calcium levels can be caused by ingesting too much calcium in one's diet, but the most common cause of a high calcium level is a parathryoid adenoma.  Measuring the level of parathyroid hormone helps to determine that a parathyroid adenoma is the cause.

Additional tests that might be performed include ultrasound exam of the neck, CT scan, MRI scan or a Sestamibi scan.  The clinical circumstances usually dictate which test is best to perform.  Of these tests, the Sestamibi scan provides specific information about the location of a parathyroid adenoma.  This test involves injecting a nuclear medicine tracer that is picked up and concentrated with parathyroid adenomas.  On imaging, one can get an idea of the location of the adenoma within the neck.  This is very useful, since the location of the parathyroid glands is variable.