Background
Limited evidence supports kidney dysfunction as an indication for parathyroidectomy in asymptomatic primary hyperparathyroidism (PHPT). We investigated the natural history of kidney function in PHPT and whether parathyroidectomy alters renal outcomes.
Methods
Patients with PHPT were compared with matched eucalcemic controls from 2000 to 2016. Estimated glomerular filtration rate (eGFR) trajectories were compared over 10 years, with cases subdivided by severity of hypercalcemia: serum calcium 2.62-2.74 mmol/L (10.5-11 mg/dL), 2.75-2.87 (11.1-11.5), 2.88-2.99 (11.6-12), and >2.99 (>12). Interrupted time series analysis was conducted among propensity-score-matched PHPT patients with and without parathyroidectomy to compare eGFR trajectories postoperatively.
Results
We studied 6,058 patients with PHPT and 16,388 matched controls. Modest rates of eGFR decline were observed in PHPT patients with serum calcium 2.62-2.74 mmol/L (-1.0 mL/min/1.73m2/year) and 2.75-2.87 mmol/L (-1.1 mL/min/1.73m2/year), comprising 56% and 28% of cases, respectively. Compared with the control rate of -1.0 mL/min/1.73m2/year, accelerated rates of eGFR decline were observed in patients with serum calcium 2.88-2.99 mmol/L (-1.5 mL/min/1.73m2/year, P<0.001) and >2.99 mmol/L (-2.1 mL/min/1.73m2/year, P<0.001), comprising 9% and 7% of cases, respectively. In the propensity score-matched population, patients with serum calcium >2.87 mmol/L exhibited mitigation of eGFR decline after parathyroidectomy (-2.0 [95% CI: -2.6, -1.5] to -0.9 [95% CI: -1.5, 0.4] mL/min/1.73m2/year).
Conclusions
Compared with matched controls, accelerated eGFR decline was observed in the minority of PHPT patients with serum calcium >2.87 mmol/L (11.5-11.9 mg/dL). Parathyroidectomy was associated with mitigation of eGFR decline in patients with serum calcium >2.87 mmol/L.
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