Spectrum of renal dysfunction after curative parathyroidectomy in symptomatic primary hyperparathyroidism

Objective: The long-term renal consequences of curative parathyroidectomy (PTX) in symptomatic primary hyperparathyroidism (sPHPT) are not well characterized. We aimed to assess renal glomerular and tubular functions in an sPHPT cohort at ≥1 year's follow-up.

Design: Retrospective-prospective study.

Methods: sPHPT patients with preoperative eGFR ≥60mL/min/1.73m² and in remission (normocalcemic) for ≥1 year after PTX underwent clinical and biochemical assessment (calcium profile, renal parameters). Ammonium chloride and bicarbonate loading tests were performed in patients with renal tubular dysfunction (RTD).

Results: Forty-eight patients (31 females) with median plasma PTH 1,029 (338-1604) pg/mL and mean eGFR 109.2±26.0mL/min/1.73m² at diagnosis were evaluated at 5.62±3.66 years after curative PTX. At follow-up, eGFR was <60mL/min/m² in 5 patients (10.4%). Patients with >10% drop in eGFR (n=31) had significantly higher pre-PTX plasma PTH (1,137 vs. 687pg/mL), and longer time to post-PTX evaluation (6.8 vs. 3.4 years). RTD was seen in 11 patients (22.9%): urinary low molecular weight proteinuria (14.6%), distal renal tubular acidosis (12.5%), hypophosphatemia (8.3%), and hypokalemia (8.3%); RTD was associated with significantly lower post-PTX eGFR (72.7 vs. 95.4mL/min/m²). Five of the 7 RTD patients undergoing loading test had impaired urinary acidification, whereas none had impaired bicarbonate resorption.

Conclusions: Reduction in eGFR and subclinical RTD were prevalent at long-term follow-up in the present Asian-Indian cohort with cured sPHPT. Further studies are warranted to understand the clinical implications of these various renal abnormalities.