Hyperparathyroidism is an overactivity of the parathyroid glands, four small glands behind the thyroid in your neck that regulate calcium levels in the blood. When one or more of these glands produce too much parathyroid hormone (PTH), calcium gets pulled from your bones and retained by your kidneys, raising blood calcium to levels that can damage multiple organ systems over time. There are three distinct types, each with different causes and treatment paths.
What the Parathyroid Glands Do
Your parathyroid glands act as a thermostat for calcium. When blood calcium drops, they release PTH, which signals your bones to release stored calcium, tells your kidneys to hold onto calcium instead of filtering it out, and triggers your kidneys to activate vitamin D so your gut absorbs more calcium from food. Once calcium returns to normal, PTH production slows down. Hyperparathyroidism disrupts this feedback loop, keeping PTH elevated even when calcium is already high.
Three Types With Different Triggers
Primary hyperparathyroidism starts in the parathyroid glands themselves. In 80 to 85% of cases, a single benign tumor called an adenoma forms on one gland and pumps out excess PTH on its own. About 10 to 15% of cases involve enlargement of multiple glands, and parathyroid cancer accounts for less than 1% of cases. The result is elevated calcium that your body doesn’t need and can’t easily correct.
Secondary hyperparathyroidism is a reaction to something else, most often chronic kidney disease. Failing kidneys can’t properly activate vitamin D or filter out phosphate. Without enough active vitamin D, your intestines absorb less calcium from food. Meanwhile, phosphate builds up in the blood. Both of these problems push calcium levels down, and your parathyroid glands respond by growing larger and producing more PTH in an attempt to compensate. The parathyroids are doing their job here, just too aggressively, because the underlying problem keeps calcium chronically low.
Tertiary hyperparathyroidism develops when secondary hyperparathyroidism has gone on so long that the parathyroid glands become permanently enlarged and start acting independently. This most commonly happens after a kidney transplant. The new kidney fixes the original problem, but the overgrown glands don’t shrink back down. They keep overproducing PTH even though calcium levels are now normal or even high.
How It Gets Diagnosed
The hallmark of primary hyperparathyroidism is high blood calcium paired with PTH levels that are elevated or inappropriately normal. Normal blood calcium falls in the range of 8.5 to 10.4 mg/dL, and normal PTH ranges from 10 to 65 pg/mL. When calcium is high, PTH should drop in response. A PTH level above 25 pg/mL in the presence of high calcium is considered abnormal. Notably, 10 to 20% of people with primary hyperparathyroidism will have PTH levels that look “normal” on paper, but those levels are still inappropriate given the elevated calcium.
Once blood work confirms the diagnosis, imaging helps locate which gland or glands are overactive before surgery. A specialized scan called 4D CT detects single overactive glands about 93% of the time, significantly outperforming the older sestamibi scan, which catches about 75% of single-gland cases. For multigland disease, detection rates drop for both methods, with 4D CT at roughly 58% and sestamibi at about 31%.
Symptoms and the Classic Pattern
Many people today are diagnosed before symptoms appear, through routine blood work that catches elevated calcium. But when hyperparathyroidism progresses, it follows a well-known pattern that doctors have traditionally summarized as “stones, bones, groans, and moans.” Kidney stones were found in 60 to 70% of patients before routine calcium screening became common. With earlier detection, kidney complications now occur in fewer than 20% of cases.
Bone loss is one of the more serious consequences. Excess PTH pulls calcium from your skeleton, and over time this leads to significantly reduced bone density, bone pain, and a higher risk of fractures. One large study found a 51% increased risk of hip fracture in people with primary hyperparathyroidism compared to those without the condition. The good news is that bone density often improves substantially after the overactive gland is removed.
Less specific but very common symptoms include fatigue, muscle weakness, brain fog, depression, constipation, and excessive thirst or urination. These tend to develop gradually, which is why many people live with them for years before getting a diagnosis.
Long-Term Risks of Leaving It Untreated
Beyond kidney stones and fractures, untreated primary hyperparathyroidism carries cardiovascular risks. Research published in JAMA Network Open found that people with untreated primary hyperparathyroidism had a higher risk of heart attack, stroke, and death compared to matched controls. Surgical treatment was associated with reduced risk, reinforcing that correction of the disease changes outcomes, not just lab values.
When Surgery Is Recommended
Surgery to remove the overactive gland or glands is the only cure for primary hyperparathyroidism. You’re typically considered a candidate if any one of these applies: blood calcium is more than 1 mg/dL above the upper limit of normal, kidney function is reduced, you have kidney stones, bone density is significantly decreased, you’re younger than 50, or you simply prefer surgery over long-term monitoring.
Modern surgery for single-gland disease is minimally invasive. Instead of exploring all four glands through a large incision, surgeons use imaging to identify the problem gland and remove it through a small opening. During the procedure, PTH levels are checked in real time. A drop of more than 50% from the pre-surgery level predicts a cure 94 to 97% of the time. Minimally invasive surgery achieves cure rates of about 99%, with complication rates around 1.2%, roughly a third of the complication rate seen with the older approach of exploring all four glands.
Management Without Surgery
If you don’t meet surgical criteria or can’t undergo an operation, monitoring and medication become the plan. Annual blood calcium and kidney function checks are recommended, along with bone density scans every one to two years at the spine, hip, and wrist. Vitamin D levels should be kept above 20 ng/mL, and calcium intake should follow the same guidelines as for anyone else, meaning you don’t need to restrict it unless specifically told otherwise.
A medication called cinacalcet can help when surgery isn’t an option. It works by making the calcium-sensing receptors on your parathyroid glands more sensitive, essentially tricking them into thinking calcium is higher than it is. This lowers both PTH and calcium levels. It’s FDA-approved for primary hyperparathyroidism when surgery isn’t feasible and for secondary hyperparathyroidism in people with end-stage kidney disease. It manages the condition but doesn’t cure it, so you’d stay on it long term.
Secondary Hyperparathyroidism in Kidney Disease
For people with chronic kidney disease, treating secondary hyperparathyroidism focuses on the underlying triggers. That means controlling phosphate levels through diet and medications that bind phosphate in the gut, supplementing active vitamin D to restore calcium absorption, and using calcimimetics to rein in PTH production directly. The goal is to slow the cycle of rising PTH and shrinking bones before the parathyroid glands become permanently overgrown.
When a kidney transplant successfully restores kidney function, secondary hyperparathyroidism resolves in most patients. But for those whose glands have grown too large and become autonomous (tertiary hyperparathyroidism), surgery to remove the overactive tissue is often the only effective option.