Background: The electronic medical record (EMR) of a large, tertiary referral center was examined to study the prevalence of undiagnosed and unrecognized primary hyperparathyroidism (PHPT).
Methods: The EMR was queried for outpatient serum calcium >10.5 mg/dL over a 2-year period.
Results: Of 2.7 million patients, 54,198 (2%) had hypercalcemia (>10.5 mg/dL). In a 2-year sample of 7,269 patients, 1.3% (95 patients) had a recorded diagnosis of PHPT, and 0.3% (16 patients) had parathyroidectomy. Of the remaining patients, parathyroid hormone (PTH) values were recorded in 32% (2,337 patients). Of patients with PTH measured, 71% (1,662 patients) had PHPT (PTH > 30 pg/mL). Patients with calcium of 11.1–11.5 mg/dL were most likely to have PHPT (55%). Patients with calcium >12 mg/dL were most likely to have PTH measured (52%). Of hypercalcemic patients, 67% never had PTH obtained, 28% of whom were likely to have PHPT. It is estimated that 43% of hypercalcemic patients are likely to have PHPT. The estimated prevalence of PHPT in the general population is 0.86%.
Conclusion: PHPT is a more common disorder than previously documented. It is crucial to evaluate even mild hypercalcemia, because 43% of these patients have PHPT. PHPT is underdiagnosed and undertreated.