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The Parathyroid Glands, Hypercalcemia, and Hypocalcemia

Linda Crampton is a writer and teacher with a first-class honors degree in biology. She often writes about the scientific basis of disease.

The thyroid gland (orange) and the parathyroid glands as viewed from the back of the body; the barred structure in the middle of the diagram is the back of the trachea

The thyroid gland (orange) and the parathyroid glands as viewed from the back of the body; the barred structure in the middle of the diagram is the back of the trachea

The Importance of Calcium in the Body

Calcium is a vital chemical in our bodies and has many functions. It's needed for muscle contraction (including the contraction of the heart muscle), nerve and brain function, bone and teeth formation, blood clotting, and many other jobs. Although an adequate amount of calcium in the blood is essential for our health, too much can be dangerous.

The parathyroid glands are small structures located in the neck behind the thyroid gland. Their job is to make parathyroid hormone, also known as PTH or parathormone. PTH stimulates body processes that increase the amount of calcium in the blood.

If too much PTH is made, hypercalcemia develops. Hypercalcemia is a disorder in which the blood contains excess calcium. On the other hand, if too little PTH is made, hypocalcemia develops. In hypocalcemia, the blood doesn't contain enough calcium. Either condition may range in severity from a minor problem to a serious disease. Luckily, treatments are available for both disorders.

Richard Owen (1804-1892) discovered the parathyroid glands by dissecting a dead rhinoceros.

Richard Owen (1804-1892) discovered the parathyroid glands by dissecting a dead rhinoceros.

The Parathyroid Glands and Their Discovery

The four parathyroid glands are usually found behind the thyroid gland, or the thyroid, which is located at the front of the neck. The thyroid is shaped like a butterfly. Occasionally, one or more of the parathyroid glands may be found inside the thyroid, in the neck above the it, or even in the chest behind the sternum or breastbone.

Although the parathyroid glands are located next to the thyroid, they are structurally and functionally distinct from it. It wasn't until 1850 that they were considered to be separate entities, however. Sir Richard Owen is credited with their discovery.

Owen was an anatomist and paleontologist. He noticed the presence of the glands when he dissected a dead Indian rhinoceros from the London Zoo, although at this point they had no name and their function was unknown. Richard Owen is also famous for his creation of the name "dinosaur" from the Greek words for "terrible lizard" and for his criticism of Charles Darwin's theory of evolution by natural selection.

Ivar Viktor Sandström was a Swedish medical student. He discovered the parathyroid glands in humans in 1880 and gave them their name. The function of the glands was established in the early 1900s after a series of experiments by different scientists.

Functions of Parathyroid Hormone

A molecule of parathyroid hormone is a protein made of 84 amino acids. Amino acids can be thought of as the building blocks of proteins. The hormone does its job by affecting the bones, the intestine, and the kidneys. In a healthy body, the level of PTH is adjusted to keep the calcium level in the blood constant. Some factors can hinder this process, however.

  • Parathyroid hormone stimulates the activity of osteoclasts, which are cells that break bone down. The process releases calcium ions into the bloodstream. (Calcium exists as ions in the body.) Other cells called osteoblasts build bone.
  • PTH increases the absorption of calcium from the digested food in the small intestine. It does this by promoting the formation of the active form of vitamin D. The vitamin helps calcium to pass from the small intestine into the bloodstream.
  • PTH stimulates calcium reabsorption in the kidneys so that the chemical isn't eliminated from the body in the urine. In the kidneys, calcium is filtered out of the blood and into the kidney tubules, or nephrons. Some is then reabsorbed further along in the nephrons and travels into the surrounding blood vessels. Any calcium that stays in the nephrons is excreted in the urine.

Parathyroid hormone also decreases the reabsorption of phosphorus in the kidney, reducing its level in the blood and increasing the amount in urine. Phosphorus travels through the blood in the form of phosphate.

A kidney contains around a million tiny tubules called nephrons. These are vital structures in the production of urine.

A kidney contains around a million tiny tubules called nephrons. These are vital structures in the production of urine.

Primary Hyperparathyroidism and Hypercalcemia

The most common cause of hypercalcemia is primary hyperparathyroidism, a condition arising from a problem in a parathyroid gland. The problem is frequently a tumor, or an adenoma. The tumor is often benign, which means that it doesn't spread through the body.

When a parathyroid gland enlarges, the additional cells produce extra PTH. This results in an elevated calcium level in the blood. The bones may weaken as PTH stimulates them to release calcium. Extra calcium may travel through the kidneys, producing kidney stones. Fortunately, a tumor on a parathyroid gland can often be removed by surgery.

Other Possible Causes of Hypercalcemia

Although a benign tumor is often responsible for hypercalcemia, there are many other possible causes of the disorder. These include:

  • some prescribed medications
  • high doses of calcium or vitamin D supplements taken for a long time
  • dehydration
  • immobilization in bed for a long time
  • kidney or adrenal gland problems
  • problems with hormones other than PTH
  • some types of inflammation
  • some kinds of cancer

In a rare inherited condition known as familial hypocalciuric hypercalcemia, the gene that codes for a calcium-sensing receptor doesn't work properly. This receptor is present in the parathyroid glands as well as in other parts of the body. Without a properly functioning receptor, the parathyroid gland isn't "told" that the blood contains calcium, so it continues to make PTH. This raises the level of calcium in the blood.

Dehydration can cause temporary hypercalcemia.

Dehydration can cause temporary hypercalcemia.

Possible Symptoms of Hypercalcemia

The following symptoms may indicate the presence of hypercalcemia, although they can also indicate other health problems. Some people who have the disorder have no symptoms, especially when the condition is mild.

  • Bone problems: pain, curvature of bones, fractures
  • Muscle problems: weakness, twitches
  • Gastrointestinal tract problems: pain, nausea, vomiting, loss of appetite, constipation
  • Kidney problems: back pain, thirst, frequent urination
  • Nervous system problems: memory loss, confusion, depression, fatigue

Since there are many different causes of hypercalcemia, treatment varies. Anyone with the disorder (or with hypocalcemia) should visit a doctor for treatment recommendations.

Hypercalcemia may lead to broken bones. The hand shown above has multiple fractures.

Hypercalcemia may lead to broken bones. The hand shown above has multiple fractures.

Hypoparathyroidism and Hypocalcemia

Hypoparathyroidism is a rare disorder in which the parathyroid glands are inactive or underactive. Two possible causes of the disorder are the removal of the parathyroid glands during thyroid gland surgery and injury to the glands during neck surgery. An autoimmune disease that attacks the glands may also cause hypoparathyroidism.

Low magnesium levels may prevent enough PTH from being made. In addition, some inherited conditions prevent the production of PTH. One of these conditions is DiGeorge syndrome. A person with this condition may be born with no parathyroid glands.

When the glands are missing or damaged, either no PTH is produced or the amount that is made is insufficient. The hormone problem causes the calcium level in the blood to fall. It also causes the level of phosphorus in the blood to rise, since phosphorus reabsorption in the kidney is no longer being inhibited.

Occasionally, the parathyroid glands are working correctly but the bones or kidneys fail to respond to PTH, resulting in a condition called pseudohypoparathyroidism. This may lead to hypocalcemia.

Possible Symptoms of Hypocalcemia

As is the case for hypercalcemia, having one or more of the following symptoms could indicate the presence of another health problem instead of hypocalcemia. If someone has unexplained symptoms that worry them they should visit a doctor.

  • tingling in the lips, fingers, or toes
  • muscle aches or cramps
  • muscle twitches
  • weakness and fatigue
  • dry skin
  • brittle nails
  • hair loss
  • headaches
  • anxiety
  • depression
  • memory loss

Complications of hypocalcemia include heart, kidney, or teeth problems, and the development of cataracts. If someone experiences hypocalcemia for a long time, calcium may be deposited in the basal ganglia of the brain.

Possible Treatments for Hypocalcemia

Calcium and vitamin D supplements in appropriate doses are often prescribed for hypocalcemia caused by hypoparathyroidism. Doctors may also prescribe specific medications to raise the blood calcium level. In addition, a diet that is high in calcium and low in phosphorus may be recommended.

A patient may have to take supplements or medications and follow a special diet for the rest of his or her life, but this routine should remove symptoms and prevent complications of the disease. As in hypercalcemia, the problems created by hypocalcemia and the patient's quality of life can very often be improved by following appropriate medical treatment.

References

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2012 Linda Crampton

Comments

Linda Crampton (author) from British Columbia, Canada on December 31, 2012:

Thank you for such a wonderful comment, drbj!! I appreciate both the comment and the vote. Happy New Year to you, too!

drbj and sherry from south Florida on December 31, 2012:

What an awesomely complete examination of the parathyroid glands, Alicia. Henry Gray who wrote 'Gray's Anatomy,' could have taken medical textbook writing lessons from you, m'dear. Outstanding and voted Up! Happy New Year, too.

Linda Crampton (author) from British Columbia, Canada on December 31, 2012:

Thank you for the visit and the comment, Eddy. I hope you have a wonderful 2013 too!

Eiddwen from Wales on December 31, 2012:

Interesting and so very useful to many I am sure. I wish you a wonderful 2013 my friend and here's to so many more hubs for us both to share on here too.

Take care

Eddy.

Linda Crampton (author) from British Columbia, Canada on December 30, 2012:

Thank you very much, Deb. I appreciate the comment!

Deb Hirt from Stillwater, OK on December 30, 2012:

This is wonderful material. Thanks for enlightening me with all the medical material. As usual, another piece well done.

Linda Crampton (author) from British Columbia, Canada on December 30, 2012:

Thank you very much for the comment, RTalloni. I certainly don't object to your linking this hub to your interesting hub about Tirosint. Thanks for the request.

RTalloni on December 30, 2012:

Thanks for an interesting look at the parathyroid gland and these disorders that can occur. Being informed is being prepared in case we need the info or in case we need to share info! I'll be linking this to my hub on Tirosint, a thyroid medication, if you have no objection.

Linda Crampton (author) from British Columbia, Canada on December 30, 2012:

Thank you so much for the comment, Bill. Happy New Year to you too!

Bill Holland from Olympia, WA on December 30, 2012:

Just another reason why I love HP...I learn the most interesting stuff in hubs like this one. Thank you for the education, and Happy New Year to you.