Four Very Small Glands that Play a Very Big Role in Our Bone Health

You already know that calcium is important for your bones, but do you know there are four tiny glands in your neck that function as the master regulators of your body's calcium? For people with osteoporosis, understanding the critical role these glands, called parathyroids, play in our bone health is a crucial piece of the bone health puzzle.

What Are Parathyroid Glands? The parathyroid glands are in the neck behind the butterfly-shaped thyroid gland. Despite their very small size (each one is typically the size of a grain of rice), their role is to continuously monitor and closely regulate the calcium in our bodies to keep it within a very narrow range, between 8.5 and 10.2 mg/dL.

What the Parathyroid Glands Do for Our Bones. Our bodies are in a constant state of "bone remodeling," where old bone tissue is broken down and new bone tissue is formed, relying heavily on calcium. The parathyroid glands, sometimes called the "calcium thermostat," help control the body's calcium balance by producing parathyroid hormone (PTH):

• Low calcium (hypocalcemia): the parathyroid glands release more PTH, signaling bones to release calcium into the bloodstream, the kidneys to excrete less calcium in urine, and the digestive tract to absorb more calcium.
• High calcium (hypercalcemia): the glands reduce PTH production, allowing blood calcium to return to normal.

The Danger of Overactive Parathyroid Glands. When one or more parathyroid glands become overactive, it's called primary hyperparathyroidism (PHPT). Secondary hyperparathyroidism is a response to another underlying condition (such as chronic kidney disease) causing low blood calcium and triggering excess PTH production.

While most osteoporosis is caused by normal aging, PHPT is another leading cause — usually from a non-cancerous adenoma on the gland causing PTH overproduction, which causes bones to release calcium into the bloodstream, weakening them. About 90% of the time only one gland is affected (less commonly two; more than two is very uncommon). Routine bloodwork often catches the hypercalcemia caused by PHPT, but unexplained symptoms like ongoing fatigue, bone/joint/muscle pain, memory issues or difficulty concentrating, increased thirst or urination, and depression or anxiety can also be related — with likelihood tied to how long hypercalcemia goes untreated.

Tests for Primary Hyperparathyroidism:

• Blood tests — hypercalcemia findings are typically retested since other conditions can raise blood calcium; PHPT is diagnosed if blood tests also show high parathyroid hormone.
• Bone mineral density test (DXA scan) — people with PHPT may show no signs other than low bone density, predominantly seen when the forearm is scanned due to the bone cell types prevalent there.
• Urine test — a 24-hour urine collection shows kidney function and calcium levels, helping determine if a kidney problem is causing the hyperparathyroidism.

Surgery is the Only Definitive Cure for Primary Hyperparathyroidism. All people, regardless of age, with PHPT will eventually develop osteoporosis if the parathyroid adenoma is not removed. Surgery to remove the overactive gland is the most common and effective treatment — a low-risk procedure that can lead to dramatic bone density improvement over time and can reverse the osteoporosis caused by this condition. If surgery is recommended, imaging (sometimes a Sestamibi parathyroid scan, using a radioactive substance taken up by overactive parathyroid glands) locates the affected gland(s).

Primary Hyperparathyroidism Is Often Underdiagnosed. PHPT is the leading cause of hypercalcemia and secondary osteoporosis, yet it's often underdiagnosed and undertreated. Balentine and colleagues reviewed over 10,000 hypercalcemia patient records and found only 32% had PTH levels measured to determine the underlying cause. Dawood and colleagues found that of 3,151 patients with persistent hypercalcemia, only 48% had PTH measured, concluding: "Within a large academic health system, more than half of patients with confirmed hypercalcemia were not assessed for PHPT, including many patients with pre-existing bone disease. Care gaps in bone mineral density assessment and medical or surgical therapy represent missed opportunities to avoid skeletal and other complications of PHPT."

In Summary. If you have osteoporosis, be aware of the role your parathyroid glands may be playing. If you or your doctor have reason to suspect a parathyroid issue, checking PTH and calcium levels is a simple and vital step toward strengthening your bones. Always consider getting another opinion — in all things, each of us must be our own healthcare advocate.

Secondary osteoporosis is a type of osteoporosis that occurs because of something other than the aging process, such as a specific underlying medical condition or medication.

Additional reading: parathyroid.com has a wealth of clearly presented information on this topic (despite the underlying marketing of their own program).

References

1. Bilezikian JP, et al. Management of Primary Hyperparathyroidism. Journal of Bone and Mineral Research 2022;37(11):2391-2403. doi:10.1002/jbmr.4682
2. Balentine CJ, et al. Failure to Diagnose Hyperparathyroidism in 10,432 Patients with Hypercalcemia: Opportunities for System-level Intervention to Increase Surgical Referrals and Cure. Annals of Surgery 2017 Oct;266(4):632-640. doi: 10.1097/SLA.0000000000002370
3. Dawood NB, et al. Systems-Level Opportunities in the Management of Primary Hyperparathyroidism: An Informatics-based Assessment. Journal of Clinical Endocrinology and Metabolism 2021;106(12):e4993-e5000. doi:10.1210/clinem/dgab540