Increasing incidence and prevalence of biochemically confirmed primary hyperparathyroidism in Stockholm, 2006-2020

CONTEXT: Primary hyperparathyroidism (PHPT) prevalence appears to be rising, but substantial underdiagnosis persist. Accurate epidemiological data are needed, requiring population-based studies using strict biochemical criteria. OBJECTIVE: To determine incidence and prevalence of biochemically confirmed PHPT in Stockholm and characterize clinical recognition and surgical management. DESIGN: Population-based healthcare cohort study using prespecified biochemical diagnostic algorithms. SETTING: Stockholm Region, Sweden, 2006-2020, using the Stockholm CREAtinine Measurements database covering two-thirds of the adult population, including ≥90% of individuals ≥65 years. PATIENTS: Adults aged ≥20 years with paired calcium and parathyroid hormone (PTH) measurements meeting biochemical criteria for PHPT. Individuals with eGFR ≤30 mL/min/1.73 m2, secondary hyperparathyroidism, or prior parathyroid surgery were excluded. MAIN OUTCOME MEASURE: Annual incidence rate and point prevalence of biochemically confirmed PHPT. RESULTS: Among 176,780 individuals contributing 578,227 PTH measurements, 10,190 patients fulfilling biochemical PHPT criteria were identified. Age- and sex-adjusted incidence rate increased from 2.81 (95% CI, 2.55-3.09) to 4.28 (95% CI, 3.98-4.59) per 10,000 person-years between 2009 and 2020, with the steepest increase among women aged ≥70 years. Prevalence increased from 0.35 to 4.76 per 1,000 individuals. Median ionized calcium was 1.39 mmol/L. Clinical diagnosis of PHPT was documented in 5,346 (52%) patients of which, 2,800 (52%) underwent parathyroidectomy, with surgery-rates stabilizing after 2013 at 4-5% annually. CONCLUSIONS: Using a large healthcare database, we observed substantially increasing PHPT incidence and prevalence, predominantly in older individuals. Only 52% received clinical diagnosis, underscoring the need for studies evaluating the long-term clinical burden of undiagnosed PHPT.