What are Parathyroid Glands?
Parathyroids are four very small glands that are approximately the size of the head of a match. They are located behind the thyroid lobes at the base of the neck. There are two glands on each side. They share the same blood vessels as the thyroid and are often intimately associated with the thyroid lobes.
The parathyroids sense the blood level of calcium and release a hormone that helps our kidneys retain calcium from the urine, release calcium from the bones and absorb calcium from the intestines. The most common problem associated with parathyroids is called hyperparathyroidism. More than 90% of the time, hyperparathyroidism is a result of a benign tumor in one of the parathyroid glands that begins to grow spontaneously and produces too much hormone. Surgical removal of this abnormal parathyroid cures the problems. Hyperparathyroidism can also be a result of the enlargement of all 4 parathyroids called hyperplasia. This condition is most commonly found in patients with renal failure. Longstanding hyperparathyroidism can lead to kidney stones, weak bones (osteopenia), and even mild psychoses where patients can be very irritable or fatigued.
Causes, Risks & Prevention
As stated earlier, renal failure can affect calcium and phosphorus metabolism, leading to hyperplasia of the parathyroids. Benign tumors called adenomas do not have a definite cause. They can be part of syndromes where multiple endocrine neoplasms can occur but these are rare. There is no way to prevent parathyroid tumors from forming. Taking calcium supplements does not increase this risk.
Detection, Tests & Imaging
Almost all cases of hyperparathyroidism are diagnosed after the detection of high levels of blood calcium. Most patients over the age of 40 will have their blood calcium measured during their annual physical exam. If the level of blood calcium is high, your physician will order a parathyroid hormone (PTH) test. If the level of the parathyroid hormone is elevated, a diagnosis of hyperparathyroidism is made. If your calcium level is more than 11 gm/dl, surgical exploration of the parathyroids is required to remove the adenoma. If the level of calcium is high but under 11 gm/dl, further testing may be needed.
If you are taking a thiazide diuretic, your physician will often ask you to discontinue that medication before rechecking your blood calcium. Thiazide diuretics can cause elevated blood calcium levels. A 24-hour urine collection sample may be needed to detect how much calcium is being lost in the urine. This helps to determine the severity of hyperparathyroidism. A bone density test can also be used to assess the risk of bone fracture; if your risk of fracture is more than 2.5 times that of the normal person, surgery to remove the abnormal parathyroid is usually required. Ultrasound of the neck is the most common imaging procedure used to find the enlarged gland or glands. A Sestamibi scan is a nuclear scan of the neck that can also help to locate an abnormal parathyroid. CT scan and MRI are not as useful. In some cases, the best technique to find the abnormal parathyroid is to just explore the neck.
Neck exploration is done through an incision in the lower neck. This is the same incision used for thyroid surgery. The thyroid lobes are rotated forward and, most of the time, all 4 parathyroids are located within a few centimeters of the inferior thyroid artery. This artery supplies blood to the lateral aspect of the thyroid and the parathyroids. The normal size of a parathyroid is 2 x 5 x 7 mm. It is usually flat and shaped like a tongue. Any rounded or enlarged gland is removed and biopsied during the surgery to confirm that it is an abnormal parathyroid. Some facilities have the ability to test the parathyroid hormone level during the procedure to determine if the blood levels have returned to normal after the removal of an abnormal parathyroid. A blue dye called Methylene blue can be given intravenously to help identify parathyroid glands during surgery but is not commonly used. Radioactive tracers can also be used to help identify parathyroids. Removing the abnormal gland or glands cures the hyperparathyroidism.
Parathyroid surgery is done under general anesthesia and the length of the procedure is determined by how difficult it is to find the abnormal parathyroid. This can take anywhere from 30 minutes to 3 or more hours for difficult cases. In rare cases, the abnormal parathyroid may not be located in the neck but in the chest behind the sternum. Exploring the neck is always the best option for finding the abnormal gland.
The recovery for parathyroid surgery is the same as for thyroid surgery. Most patients take only Tylenol (acetaminophen) or Advil (ibuprofen) for pain. Normal activity can be resumed very promptly after surgery, usually within 72 hours. Full recovery can be expected at 2 to 3 weeks.
Most patients will be sent home with a calcium supplement such as TUMS® antacid (calcium carbonate). When hyperparathyroidism is cured by surgery, patients may experience hungry bone syndrome (low blood calcium). Taking the calcium supplement ensures that adequate calcium is available to be absorbed from the intestines to replace the bone losses. Some patients will experience cramping of their legs, feet or hands and could also have tingling around their mouth or eyes. These are symptoms of low calcium and should be reported to your surgeon. In some cases, treatment may require intravenous calcium. The calcium supplement taken by mouth is only required for a few weeks and can then be discontinued.