Normocalcemic Primary Hyperparathyroidism

Michael Yeh here from UCLA here to talk about Normocalcemic Primary Hyperparathyroidism (NCPH).

This is a condition where the blood calcium level remains normal—typically between 8.5 and 10.3 mg/dL—while the parathyroid hormone (PTH) level is elevated, usually 65 pg/mL or greater. It’s an uncommon diagnosis because we don’t often check PTH levels in people with normal calcium levels. The exception might be if a patient is found to have unexplained bone loss or osteoporosis, in which case a doctor might check PTH levels, even when the calcium is normal.

Key Diagnostic Considerations:

NCPH can only be diagnosed once other causes of secondary hyperparathyroidism have been ruled out. The most common secondary causes include:
- Vitamin D deficiency (typically a vitamin D level below 20 ng/mL).
- Kidney disease, which can also elevate PTH levels.

Once we’ve ruled out vitamin D deficiency and kidney disease, and a patient has normal calcium (usually in the 9s or low 10s) along with an elevated PTH level, then we can consider the diagnosis of normocalcemic primary hyperparathyroidism.

Treatment Considerations:

If your calcium level is below 10 (somewhere in the 9’s), surgery is usually not necessary. There is no clear evidence in the medical literature showing that surgery improves outcomes for patients with calcium levels in this range.
However, if your calcium level is in the 10-10.3 mg/dL range and your PTH level is elevated (e.g., 100 pg/mL), surgery may be beneficial. This is because this picture starts to resemble the profile of classic primary hyperparathyroidism, where surgery is typically recommended.
Surgery is more likely to be considered if there is a clear evidence of bone loss, such as in cases of osteoporosis or osteopenia (an earlier stage of bone loss).

Symptoms and Surgery:

Patients often ask if surgery will help with nonspecific symptoms like fatigue or difficulty concentrating. These symptoms are not specific to NCPH and could be caused by many other factors. There’s no clear evidence that surgery improves these symptoms, especially for patients with calcium levels below 10.
For those with calcium in the low 10s (10-10.3), surgery might help strengthen bones and reduce the risk of fractures, especially if osteoporosis is present.
Calcium levels of 10.4 and above reflect classic primary hyperparathyroidism, which should usually be treated surgically.

Final Thoughts:

NCPH is a nuanced diagnosis. If you’re diagnosed with this condition, it’s important to consult with an endocrinologist or endocrine surgeon. Take time to understand your options and don’t rush into surgery. This condition is typically not immediately dangerous, and careful, informed decision-making is key.