Parathyroid Gland Dysfunction 

Last week, we discussed what our parathyroid glands do for us when they are working properly. This week, we are exploring what happens when they malfunction. As a quick recap, parathyroid glands are responsible for regulating the calcium level in our blood. To be more specific, they help increase the calcium level in our blood if it gets too low (the same way a heater raises the temperature in our house).

So, what happens if one or more parathyroid glands start working incorrectly? There are two ways this happens: overactive parathyroid glands and underactive parathyroid glands. The majority of this article will be about overactive parathyroid glands, for reasons explained later.

Overactive Parathyroid Glands

Occasionally, one or more parathyroid glands will become overactive and produce too much parathyroid hormone (PTH). This is called hyperparathyroidism, which simply means a condition in which there is too much parathyroid hormone. This happens a few different ways, but the overwhelming majority is because a parathyroid gland “breaks” and functions inappropriately (primary hyperparathyroidism). We will also discuss secondary and tertiary hyperparathyroidism, although these make up a small majority of overactive parathyroid glands.

Overactive Parathyroid Glands: Primary Hyperparathyroidism

In primary hyperparathyroidism, the problem is in the parathyroid glands. One or more of the glands are overactive simply because they are broken, most commonly caused by a parathyroid adenoma. They over-produce PTH the same way a faulty thermostat tells the heater to pump out more heat even though the house is 85 degrees. Since the purpose of PTH is to raise the calcium level in the blood, the excess PTH leads to elevated calcium. This is the only condition that leads to elevated calcium and elevated parathyroid hormone levels at the same time!

Excess PTH and calcium cause problems in several different ways. Excess PTH acts on the bones and increases bone remodeling. While this includes both creation and breakdown of bone, sustained elevations in PTH lead to a net bone loss. This loss of calcium (along with phosphate, which is important later) leads to demineralization of bone. You probably know this better as osteoporosis, or the milder form, osteopenia. While this can be noted on bone density or DEXA scans, it is not something you feel. But this excess turnover does cause bone pain. This pain can be in any bone, and is often felt in different areas.

The remainder of the effects are caused by the elevated calcium. The next major site of impact is the kidneys. If the parathyroid glands are the “heater” side of calcium regulation, the kidneys are the “A/C” side. The kidneys process the extra calcium in the blood and put it into the urine. This is important for two reasons: the kidneys have to work harder to keep up which leads to damage to the kidneys, and the excess calcium in the urine leads to the development of kidney stones.

Another, often less talked about site of damage is the cardiovascular system. The excess calcium leads to an increased risk of hypertension, arrhythmias (abnormal heartbeat), heart attack, and stroke.

Finally, the excess calcium can affect people in ways that cannot be measured. This includes issues with energy, mood, sleep, focus, concentration, memory, hair loss, reflux, and headaches. These symptoms vary widely between patients and have little correlation with calcium or PTH levels.

A question you might be thinking right now is why this happens, or how do you prevent it from happening to you? Sadly, while we know what happens in patients with primary hyperparathyroidism, we don’t know why it happens in the over-whelming majority. In these cases, there is no preventative measure you can take, nor is there anything you did or that was done to you to cause this.

Overactive Parathyroid Glands: Secondary and Tertiary Hyperparathyroidism

Primary hyperparathyroidism is caused by overactive parathyroid glands that are misbehaving. Secondary hyperparathyroidism is an overproduction of PTH by the parathyroids that is a response to something else that is misbehaving. This can be broken down into two groups: bad kidneys and low vitamin D. The important factor in both of these situations is this: your calcium is low! Vitamin D is produced by the kidneys, activated by PTH, and acts on the intestines to absorb calcium. Need more calcium? The body will increase PTH to increase vitamin D activation and therefore calcium absorption. If the kidneys are failing, vitamin D production falls behind. As the kidneys continue to fail, phosphate (the one that binds with calcium to mineralize bone) will not be removed from the body, and will further lower calcium levels. To try to fix this, PTH secretion with be increased by overactive parathyroid glands. This overproduction of PTH is caused by a problem outside of the parathyroid glands. (Interestingly, vitamin D deficiency can be caused by primary hyperparathyroidism. This can lead to issues with diagnosis and referral.)

After years of poor kidney function, including years of dialysis, parathyroid glands will get so used to the overproduction of PTH, that they will become abnormal themselves. This is the development of a parathyroid gland problem (1º hyperparathyroidism) on top of a kidney problem (2º hyperparathyroidism, 1 + 2 = 3). It is only an issue for patients on dialysis.

Under-active Parathyroid Glands

Under-production of PTH is almost always an issue caused by previous neck surgery, specifically thyroidectomy or parathyroidectomy. These patients will have both low calcium and PTH levels. There are a very small minority of patients who have low parathyroid function from birth, but there are other signs that would be noted first. The only other notable group with under-active parathyroid glands are those with high calcium levels for some other reason. In these cases, the PTH level will be low or even undetectable when the calcium level is high. Unlike every other group mentioned, patients falling in these categories will never need a parathyroid operation.

Overactive Parathyroid Glands: What’s Next?

Now that you know more about the parathyroid glands are and how they misbehave, the next step is determining whether or not they are misbehaving. Tune in next week to find out about how we diagnose overactive parathyroid glands with Dr. Dan Ruan.

Additional Resources:

• Learn more about the Norman Parathyroid Center.
• Read more on the Parathyroid blog.
• Become our patient.
• Check out our sister surgeons at the Clayman Thyroid Center, the Scarless Thyroid Surgery Center and the Carling Adrenal Center. We are now united under one roof, operating at the Hospital for Endocrine Surgery.