Most people (80%) have four parathyroid glands (range one to ten), two on each side which are located on the underside of the thyroid gland, share a blood supply with the thyroid and are often adherent to the gland or occasionally embedded within the thyroid gland.
The glands are normally pea sized and appear very similar to normal lymph nodes. Parathyroid glands produce Parathyroid Hormone (PTH) which can be measured in the blood stream. PTH participates in control of calcium metabolism with in the body helping to maintain the calcium levels in the blood stream by directing uptake of calcium from the food during digestion or by pulling calcium out of the bones.
This uncommon condition results from the overproduction of parathyroid hormone (PTH) by the parathyroid gland(s). This can occur due to kidney problems altering the parathyroid glands (secondary and tertiary hyperparathyroidism) or due to a specific problem with the parathyroid gland(s) (primary hyperparathyroidism). The most common form of primary hyperparathyroidism results from a benign tumor (adenoma) on one gland (96%). Rarely there is an adenoma of more than one gland (1%) or there is enlargement of all four glands (3-4%) called hyperplasia.
Symptoms of hyperparathyroidism are known as "moans, groans, stones and bones". In cases of mild hyperparathyroidism there are few symptoms but patients may complain of fatigue, depression, aches and pains. The elevated PTH pulls calcium out of the bones causing osteoporosis or osteopenia, bone weakness and bone pain. There is also an elevation of calcium secreted in the urine which may cause calcification in the kidney and kidney stones. This may cause pain and kidney dysfunction. Very high levels of calcium in the blood stream may cause stomach ulcers, pancreatitis and nervous system issues. Many of these symptoms are reversible within months of treating the underlying problem.
When a patient has chronically elevated blood calcium levels or kidney stones an evaluation for hyperparathyroidism is appropriate. Blood testing including a regular and ionized calcium, PTH and Vitamin D levels are combined with a 24-hour urine collection for calcium. If hyperparathyroidism is suspected the degree of severity should be evaluated with bone density testing and possibly kidney imaging for stones.
When laboratory testing suggests hyperparathyroidism it is appropriate to try to localize the enlarged parathyroid with imaging studies. Neck ultrasonography is non-invasive and gives critical information about the overlying thyroid gland and will often show an enlarged mass behind the thyroid consistent with an enlarged parathyroid gland. Nuclear medicine imaging (sestamibi scan) uses a radiotracer which is taken up by the parathyroid cells more actively than the surrounding tissues (thyroid) and stays in the parathyroid glands longer. Thus scanning immediately and in a delayed fashion can help distinguish parathyroid from thyroid uptake. Normal parathyroid glands do not take up enough tracer to be imaged, enlarged glands will often show uptake (75-95% of the time). There are other methods to localize the abnormal gland but these are currently the most reliable.
Very early forms of hyperparathyroidism may have few or no associated symptoms. The process may not have persisted long enough to cause bone or kidney changes as the PTH level is not yet profoundly elevated. These cases are usually associated with smaller adenomas where the gland is too small to image. In some instances it may be appropriate to consider observation in this setting to allow the disease to progress until the gland is large enough be imaged. Typically, however, treatment is indicated once the problem is identified.
Treatment of primary hyperparathyroidism is the surgical removal of the offending parathyroid gland(s). A person needs at least one functioning parathyroid gland to meet hormonal requirements post removal. Thus the removal of glands should be minimized to include only disease glands. Recent advancements include the gland localization by imaging as described above, the development of the ability to measure PTH blood levels during surgery and of newer minimally invasive surgical techniques. Some also find the use of radioactive tracers and intraoperative probes beneficial.
If the offending parathyroid has been localized with imaging prior to surgery a limited surgical procedure is often appropriate. The use of intraoperative ultrasonography confirms the enlarged gland location for the surgeon. A small incision is performed and the use of endoscopes can help to minimize the dissection of tissues. The gland is carefully identified and removed. Blood levels of PTH are checked prior to gland removal and 5 and 10 minutes after removal. An appropriate drop in PTH level combined with frozen biopsy of the removed gland confirms the successful treatment of the problem in most cases. This procedure can be performed under local anesthesia if desired and is usually an outpatient procedure.
If the intraoperative PTH level does not drop as much as expected then more than one gland is involved and a full exploration is indicated (see below). Very occasionally (<5%) the PTH level does drop appropriately but then elevates again in the months after surgery. This suggests a second gland is involved but was much smaller than the original enlarged gland.
In the setting where the offending gland may not be identified or more than one offending gland is suspected, a larger surgery is indicated. This involves a full exploration of both sides of the neck to identify all four glands. A comparison is then made visually to determine which appear abnormal and PTH levels are monitored after removal to confirm adequate treatment. Again, one gland (or a portion of one in the setting of hyperplasia) must remain to provide enough hormone production. Challenges to this surgery may include an abnormal number of glands (one to ten), abnormal location of the glands (high in the neck to low in the chest) and scar tissue from prior surgery.
Fortunately complications from parathyroid surgery are infrequent (<1%) particularly with the minimally invasive approach. Possible problems include injury to the nerve to the vocal cord causing hoarseness, trauma to the remaining parathyroid glands causing hypoparathyroidism (low PTH and blood calcium levels) which may be temporary or permanent and missing an abnormal gland which could require repeat surgery.