High calcium is almost always caused by parathyroid disease (specifically, primary hyperparathyroidism), but just knowing a calcium level is not enough for a definitive diagnosis. We also need to see a PTH level. Once you have a calcium and PTH level together (ideally taken from the same day), you can usually make the diagnosis. A high calcium combined with a high or normal PTH is diagnostic of primary hyperparathyroidism in most cases. For help with this, check out the Parathyroid Disease Analysis App.

Regarding primary parathyroid disease: Primary hyperparathyroidism is the most common form of parathyroid disease, and when people talk of “parathyroid disease” we are usually referring to primary hyperparathyrodism. But secondary hyperparathyroidism should be recognized also. Some web sites on parathyroid disease are focused heavily on primary hyperparathyroidism, to the point where “parathyroid disease” becomes synonymous with “primary hyperparathyroidism.” On this site, I want to distinguish and explain the different forms, since secondary and primary hyperparathyroidism are often confused.