What causes hypercalcemia in primary hyperparathyroidism?

Updated: Oct 02, 2018
  • Author: Lawrence Kim, MD, FACS, FACE; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Answer

Answer

The causes of hypercalcemia that result in a concomitantly elevated parathyroid hormone level are few. These include familial benign (hypocalciuric) hypercalcemia (FHH) (see Related disorders), lithium-induced hypercalcemia, and tertiary hyperparathyroidism. A minority of patients (ie, 10-15%) with hyperparathyroidism have parathyroid hormone levels at the high end of the reference range, though inappropriately high in the presence of elevated serum calcium concentrations. A subset of patients have calcium levels within the reference range with elevated parathyroid hormone, so-called normocalcemic hyperparathyroidism. However, when considering this diagnosis, all potential causes of secondary hyperparathyroidism (eg, low calcium intake, gastrointestinal disorders, renal insufficiency, vitamin D deficiency, hypercalciuria of renal origin) should be excluded. Patients with normal calcium levels and elevated parathyroid hormone levels in the absence of an identifiable secondary cause should be monitored for progression to hypercalcemia.

Secondary and tertiary hyperparathyroidism are typically diagnosed based on their clinical context. Cancer-induced hypercalcemia is usually associated with a low parathyroid hormone level but possibly a high parathyroid hormone-related peptide level.


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