Hyperparathyroidism

Hyperparathyroidism (HPT) occurs when one or more parathyroid glands enlarge and produce too much parathyroid hormone. The extra amount of parathyroid hormone tricks the body into thinking that the level of calcium in the blood is too low. As a result, calcium moves into the bloodstream from places in the body where it is normally stored, namely the bones. This movement of calcium into the bloodstream has several undesirable consequences. First, the level of calcium in the bloodstream will become too high, causing a condition known as “hypercalcemia.” Second, over time too much borrowed calcium from bones can cause weakness and thinning of the bones (osteoporosis), which may even cause bones to break. Third, excess calcium can form stones in the kidneys.

In over 90% of patients, HPT is caused by a single, benign (non-cancerous) tumor called an “adenoma” in one of the four parathyroid glands. Occasionally patients with HPT have parathyroid hyperplasia - a condition involving benign growths in more than one parathyroid gland. Most patients with parathyroid hyperplasia have a hereditary form of HPT, such as multiple endocrine neoplasia.

HPT Symptoms

Up to 80% of patients with HPT have no obvious symptoms, which are similar to other common conditions such as menopause, mid-life crisis, stress, depression and even early dementia. Symptoms may include:

• Low energy
• Feeling tired (fatigue)
• Loss of appetite
• Muscle weakness
• Bone or joint pain
• Constipation
• Anxiety

Patients with HPT may also have kidney stones, bone loss and/or digestive complaints. Untreated HPT may cause nausea, vomiting and abdominal pain as well as more serious problems such as osteoporosis, bone fractures, memory loss and depression.

Diagnosis

HPT is usually diagnosed by a blood test that measures calcium levels in the blood. Sometimes HPT is discovered unexpectedly during routine checkups when a blood test reveals high calcium levels. Patients may be surprised to find they have HPT, especially if they feel well.

An additional blood test to measure the level of parathyroid hormone ("intact PTH assay") will be needed to make sure the patient has HPT, because this is only one cause of a high calcium level in the blood.

Other tests will likely include:

• A 24-hour urine collection to measure the amount of calcium in the urine
• An X-ray and/or ultrasound of the kidneys to search for kidney stones
• A bone density test is recommended for all patients with HPT

Sestamibi Scan

Once a patient is diagnosed with HPT, other imaging tests may be done to identify how many tumors are present and their location. The best test for this is the sestamibi scan, which involves a radioactive agent called “technetium sestamibi” given intravenously, which is absorbed by abnormal parathyroid glands.

A sestamibi scan is usually done along with an ultrasound study, but both tests may fail to identify a parathyroid adenoma in 10 to 20% of patients. Therefore, other tests sometimes need to be done. Additional tests may include magnetic resonance imaging (MRI), computerized tomography (CT scan) and venous sampling.

Treatment

A parathyroidectomy (surgical removal of the parathyroid) is currently the only way to cure HPT, although surgery may not be necessary for patients with a mild form of the disease. This is because most mild cases (about 75%) of HPT do not worsen over time. There are two ways to perform a parathyroidectomy: 

Conventional Parathyroidectomy

In a conventional parathyroidectomy, patients are given general anesthesia. The surgeon examines all four parathyroid glands during surgery. Rarely, the abnormal gland(s) cannot be found and more extensive surgical exploration is needed. For example, the abnormal gland may be located inside the thyroid gland, thymus gland or upper mediastinum (the front part of the chest). When this happens, part of the thyroid or thymus may be removed or the upper mediastinum may need to be explored.

Minimally Invasive Parathyroidectomy

When the location of the abnormal parathyroid gland(s) is known ahead of time, the surgeon may be able to use a minimally invasive approach during surgery. This involves the removal of the abnormal parathyroid gland(s) without examining the other glands. The benefits of this approach may include a shorter hospital stay (generally four hours or less) and sometimes a smaller incision.

In about 5% of cases, the abnormal parathyroid gland is not easily found during minimally invasive surgery. If this happens, the surgeon may need to switch the patient to general anesthesia so that other parts of the neck can be explored.

Surgical Guidelines

The best candidates for HPT surgery have:

• Symptoms of HPT
• Kidney stones
• Evidence of bone disease
• Severe hypercalcemia

If no symptoms are present, surgery can also be indicated for patients with:

• A calcium level in the blood that is more than one mg/dL above the normal level
• A calcium level in urine that is more than 400 mg/day
• Significant kidney dysfunction (reduction in creatinine clearance of 30% or more)
• Osteoporosis
• Young age (less than 50 years)

Although the doctor will use these guidelines to plan the best treatment for a patient, both the patient and doctor should be comfortable with the final treatment decision.