Parathyroid Function and Anatomy
The human body is truly an amazing machine. One of the most fascinating aspects of physiology is the mechanism by which the body can store calcium and mobilize the mineral for use. Calcium is vital to the proper functioning of our nerve and muscle cells, and therefore allows us to control voluntary functions such as walking, eating, and speaking. It also plays a crucial role in involuntary functions, such as swallowing, digestion, the contraction of our hearts, and thinking, among others. Our skeleton supports our muscles and houses our internal organs, and, interestingly enough, also serves as a reservoir for the calcium that we consume from the food that we eat.
How do we get calcium from the bone to our nerve and muscle cells? An important component of the endocrine system is the parathyroid tissue which is located adjacent to another endocrine gland, our thyroid gland. Parathyroid glands secrete parathyroid hormone (PTH) which enters the blood stream and travels to the bone and activates cells that, in turn release or mobilize calcium from the bone into the blood stream. The calcium then allows the nerve and muscle cells to perform their necessary functions.
Most humans have two paired parathyroid glands on either side of the midline of the neck, located behind or next to the thyroid glands. The exact location of the glands can vary greatly, and can even be found behind the esophagus, next to the carotid artery, below the jaw, or even in the chest.
As is the case with the thyroid gland, the parathyroid glands can be underactive or overactive. Underactive glands are not very common and can result from trauma (surgical or non-surgical), radiation therapy for other conditions, or some rare medical problems.
More commonly, the parathyroid glands can become overactive and the condition is referred to as hyperparathyroidism. There are several types of hyperparathyroidism, but the unifying theme is that excess PTH is secreted into the blood, which can lead to bone loss (osteoporosis), depression, kidney stones, nausea, vomiting, abdominal pain, muscle pain, urinary frequency, and other signs/symptoms.
Hyperparathyroidism is a surgical disease and typically requires removal of overactive tissue for a cure. Surgery typically involves removal of one or more glands through an incision over the windpipe, just above the breastbone.
If your doctor believes that you have hyperparathyroidism which may benefit from surgery, you will undergo a series of tests in order to achieve “localization.” Localizing overactive parathyroid tissue is very helpful, as it can help target the abnormal gland and direct the surgery to a specific side of the neck and help to decrease operative time and risk to adjacent structures.
We perform an ultrasound in the office to help identify the abnormal gland(s). This is important, as ultrasonography is operator-dependent and surgeons understand where we should look most commonly to discover the location of the diseased gland.
CT/MRI can be performed in radiology departments and can be helpful adjuncts to ultrasonography, as they can provide more detail of the soft tissues in the neck. Nuclear medicine scanning can also help to localize an abnormal gland by utilizing the fact that parathyroid tissue retains certain radioactive materials for a longer amount of time then surrounding structures. The scans can often help to localize an abnormal parathyroid gland and guide the surgeon’s hands to the correct location.
Rapid parathyroid hormone testing (Intra-operative PTH).
Several years ago, we were able to successfully institute rapid parathyroid hormone testing at the hospitals to which we are affiliated. Rapid PTH testing utilizes the fact that the PTH level drops precipitously after the diseased parathyroid tissue has been removed from the body. During surgery, the blood can be sampled via a small vein in the neck or an IV catheter in the arm. After the parathyroid gland is located and removed, we can draw blood to ensure that the parathyroid hormone level in the blood decreases. The hormone is cleared very rapidly from the blood, so the decrease can be detected fairly quickly. We use rapid PTH testing in conjunction with surgical removal to confirm that an abnormal parathyroid gland has been removed. The parathyroid hormone level in the blood should decrease after the overactive gland has been removed.
If parathyroidectomy is indicated, you will meet with the surgeon and discuss the operative plan. Typically, parathyroid surgery is accomplished through a small incision made between the breastbone and the Adam’s apple. The surgery typically takes between one and several hours. If there is only one enlarged gland, and it is found expeditiously, then surgery can take as little as 15-30 minutes. If the surgical dissection is limited, it is possible that you can expect to go home immediately following the procedure. Some patients will require an overnight stay if there is a more extensive dissection.
It is possible that the remaining parathyroid glands need to regain normal function, and therefore low parathyroid function can occur post-operatively. There is also a phenomenon known as “hungry bones syndrome” which can also affect calcium metabolism after surgery. This is due to calcium-starved bone aggressively scavenging available calcium from the blood when the PTH levels return to normal. The consequence of these post-operative states is that the blood calcium level is low, and supplementation is required until function returns back to a normal state.
Most patients have minimal pain after the procedure and some may only require a few doses of Tylenol or a mild narcotic medication for pain. Long-term side effects are rare and most patients are fairly well-healed within a few weeks.