NORMAL PARATHYROID FUNCTION

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What do the parathyroid glands do?

How do the parathyroid glands control the calcium level in my body?

 

What do the parathyroid glands do?

Parathyroid glands control the level of calcium in your body.  There are four of them, two on each side of the neck behind the thyroid gland.  Many patients confuse the word “parathyroid “ with “thyroid”.  The only real connection they have to one another is their location in the neck.  The “para-“ in “parathyroid” means “next to”, hence, the term simply means that the parathyroid glands are located “next to the thyroid gland”.  I sometimes simply call them the “calcium glands” in order to avoid this confusion.

How do the parathyroid glands control the calcium level in my body?

The four parathyroid glands are tiny when normal, usually about the size of a baby aspirin, located just behind the thyroid gland.  They monitor the level of calcium in the blood stream.  When the level of calcium is low, they are “turned on” to produce their hormone, PTH.  This PTH (which stands for “parathyroid hormone”) causes your body to retrieve calcium back into the blood stream from wherever it can.  If you have calcium in your diet, your intestines will increase their absorption of calcium.  Calcium that has been deposited in the bones will be re-absorbed back out into the blood.  Once the calcium level has normalized, the PTH level drops back down.

In the normal situation, the calcium level remains balanced between about 8 and 10.  The calcium in your bones stays put, and if you add calcium to your diet, it gets transferred to your bones or is filtered out by the kidneys without elevating the level of calcium in your bloodstream out of this normal range.

The control of calcium is very important to the body, since there are so many important functions that depend on the appropriate concentration of calcium in the blood.  If the serum calcium level becomes too low or too high, the function of several of these processes can be impaired. This includes the processes within the nervous system, the proper function of your muscles, and of course the skeleton, which must maintain a sufficient calcium level to provide adequate strength.

There are other feedback systems in the body that contribute to keeping a proper balance of calcium in the blood and in the bones. Vitamin D is the most important other substance that is involved in calcium balance.  It functions alongside of PTH to maintain the calcium level in the appropriate range. But by comparison, PTH is the more important regulator. Vitamin D is a more passive mechanism, but still important. Its significance is much greater in patients who have a low calcium level, and in patients with chronic kidney disease. Endocrinologists are paying more attention to vitamin D these days, however, in the setting of hyperparathyroidism, there is quite a bit of misunderstanding even among specialists about the role of vitamin D. You can read more about this on the “Diagnosis of Hyperparathyroidism” page.

hunt-for-the-parathyroids-coverIf you really want to learn more about the parathyroid, there is an excellent book recently published, explaining the history of how and when we learned what we now know about the parathyroid glands, starting way back in the 1850’s when the gland was first discovered in a rhinoceros.  Although it was identified then, it took decades before anyone understood it’s control over calcium, and the history of the series of discoveries makes for interesting reading.  Here’s a picture of the front cover, and if you wish to order, here’s a link to Amazon.  The author is a doctor, Jörgen Nordenström.

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