Parathyroid disorders may result from a number of factors. The causes of hyperparathyroidism tend to be very different from those of hypoparathyroidism.

Possible causes of hyperparathyroidism include:

• Adenomas. Benign (noncancerous) tumors. An adenoma on a parathyroid gland can cause it to become overactive. Most cases of hyperparathyroidism result from a single adenoma, but some patients have more than one. Adenomas cause 85 percent of cases of primary hyperparathyroidism, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).
  
  
• Parathyroid hyperplasia. Enlargement of the parathyroid glands. This enlargement makes the glands release additional parathyroid hormone (PTH).
  
  
• Parathyroid cyst or cancer. Both are rare, but can cause the excretion of excess PTH.
  
  
• Genetic defects. In some cases, hyperparathyroidism may occur in families, indicating a possible genetic link. Familial hypocalciuric hypercalcemia is a form of hyperparathyroidism that is linked to an identified genetic mutation. As a result of the mutation, the parathyroid glands are unable to detect calcium in the blood and continually release PTH.
  
  
• Radiation. Exposure to radiation, especially when the patient is young, is thought to contribute to hyperparathyroidism.
  
  
• Multiple endocrine neoplasia type 1 (MEN1). A rare, inherited group of conditions. Growths occur on the parathyroid glands, making all four overactive. In addition to hyperparathyroidism, MEN1 may also cause other endocrine disorders, such as insulinoma, an insulin-producing tumor of the pancreas.
  
  

Certain medications may also cause or worsen hyperparathyroidism. Lithium, used primarily to treat bipolar disorder (manic depression), can alter the body’s use of calcium and its response to PTH, leading to hyperparathyroidism. In addition, thiazide diuretics, used to treat high blood pressure and other conditions, may also aggravate hyperparathyroidism.

Hyperparathyroidism may also be the result of other conditions, in which case it is known as secondary hyperparathyroidism. Causes of secondary hyperparathyroidism include chronic kidney failure, absorption disorders of the intestines and kidneys, and rickets (a bone disease related to insufficient vitamin D). Patients on long-term hemodialysis, the most common treatment for chronic kidney failure, may be at additional risk.

Women are twice as likely than men to develop hyperparathyroidism, according to the National Institutes of Health. Additionally, the risk of developing hyperthyroidism increases with age, with most cases first identified in patients older than 45 years.

Hypoparathyroidism is rare and most often results from damage to parathyroid glands after surgery or traumatic injury to the neck area. For example, hungry bone syndrome is a condition in which the bones conserve calcium in an effort to heal after removal of the parathyroid glands (parathyroidectomy), resulting in hypoparathyroidism. Certain treatment methods for hyperparathyroidism, such as radioactive iodine treatment, can also cause hypoparathyroidism.

Other causes of hypoparathyroidism can include:

• Autoimmune diseases. In some cases, the body creates antibodies that attack the parathyroid glands. This may damage the glands and render them dysfunctional.
  
  
• DiGeorge syndrome. A congenital condition in which the patient is born without parathyroid glands. DiGeorge syndrome also causes heart and immune system problems.
  
  
• Low levels of magnesium in the blood. This can interfere with the ability to produce PTH.
  
  
• Type 1 autoimmune polyglandular syndrome. A cause of familial hypoparathyroidism. This is a disease in which the immune system attacks the endocrine system. Patients may also have Addison’s disease, other autoimmune diseases and chronic yeast infections.
  

Parathyroid disorders are frequently diagnosed in patients who have not noticed any signs or symptoms of the disease. The disorders are often detected due to atypical results of blood tests performed for other reasons.

Blood tests that show abnormal levels of calcium, parathyroid hormone (PTH), phosphorus and magnesium may indicate a parathyroid disorder. For example, high levels of calcium and PTH and low amounts of phosphorus usually indicate hyperparathyroidism. Conversely, low levels of calcium, PTH and magnesium in the blood indicates hypoparathyroidism.

If a patient’s calcium levels are high, physicians may also perform tests to rule out other causes, such as vitamin D intoxication, sarcoidosis (a disease marked by formation of inflammatory lumps in organs), hyperthyroidism, adrenal failure, prolonged immobilization and certain cancers.

Additional methods may confirm the diagnosis of a parathyroid disorder and the effect the disease has had on the body. These may include:

• Urine tests. Patients may be asked to collect samples of their urine over a 24-hour period. An analysis of these samples may be able to measure the amount of calcium being excreted, as well as provide information about possible kidney damage or the formation of kidney stones. Other tests of kidney function may also be ordered, such as glomerular filtration rate.
  
  
• Imaging tests. A variety of procedures, including ultrasound, may be used to locate and measure the size of the patient’s parathyroid glands, as well as to look for tumors. A sestamibi scan is a nuclear medicine scan that may help to localize a parathyroid tumor. Bone density tests such as a DEXA scan (dual-energy x-ray absorptiometry) can detect the osteoporosis that may result from hyperparathyroidism.
  
  
• Electrocardiogram (EKG or ECG). Hypoparathyroidism may cause abnormal heart rhythms that are detectable with an EKG.
  

Treating parathyroid disorders is possible and in many cases will relieve the patient’s symptoms. The treatment depends on whether the patient has overactive (hyper) or underactive (hypo) parathyroid glands. The treatment method also depends on whether there is an underlying cause, such as kidney disease.

Patients with hyperparathyroidism may have few if any symptoms and may choose not to undergo treatment. In such cases, long-term monitoring is recommended to detect any changes in their condition that may require treatment. During this period of monitoring, physicians may make some of the following recommendations to prevent the condition from worsening:

• Drink adequate water
  
• Get frequent exercise
  
• Make and keep regular medical appointments
  
  

Patients at risk of complications such as osteoporosis may be prescribed preventive medications such as bisphosphonates.

Patients should make sure each of their physicians knows about their condition. Some therapies for other disorders may worsen the symptoms of hyperparathyroidism. These include certain types of diuretics, medications with lithium, prolonged bed rest and high-calcium diets.

In both hyperparathyroidism and hypoparathyroidism, patients should consume appropriate amounts of calcium and vitamin D. Hypoparathyroidism is most often treated with supplements of calcium and vitamin D. In the rare cases where hypoparathyroidism is permanent, these supplements are required for the rest of the patient’s life. However, it is important that patients do not self-medicate with calcium or vitamin D supplements as excess levels can result in additional complications.

In general, parathyroid disorders cannot be prevented. After undergoing thyroid or neck surgery, the physician may recommend that the patient watch for early indicators of hypoparathyroidism. Early detection of signs or symptoms can lead to early treatment with dietary supplements, which may reduce the risk of complications.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their condition. Patients may wish to ask their doctor the following questions about parathyroid disorders:

1. What type of parathyroid disorder do you think I have?
   
   
2. How do you know I have a parathyroid disorder if I have no symptoms?
   
   
3. Could there be other causes of my condition?
   
   
4. Are additional tests needed to confirm the diagnosis? If so, do I need to do anything to prepare for them?
   
   
5. What may have caused my parathyroid disorder?
   
   
6. If I have no symptoms now, when might they appear and how severe will they be?
   
   
7. What are my treatment options and their risk and benefits?
   
   
8. What changes in diet and exercise should I make because my disorder?
   
   
9. Should I be monitored for possible complications such as osteoporosis? What tests might I need, and how often?
   
   
10. Is it safe for me to get pregnant if I have an asymptomatic parathyroid disorder?
    
    
11. Are others in my family likely to develop this disorder? If so, should they have any screening tests or regular monitoring?