Glomerular Filtration Rate and Parathyroid Hormone Secretion in Primary Hyperparathyroidism

Abstract

Context: The recent Third International Workshop on the Management of Asymptomatic Primary Hyperparathyroidism (PHPT) set 60 ml/min as the precise level of glomerular filtration rate (GFR) below which surgery is recommended because it is considered a threshold of concern in patients with PHPT. Objective: The aim of the study was to investigate the relationship between different stages of renal insufficiency and PTH levels in PHPT patients. Design: We conducted a cross-sectional study. Patients and Methods: We studied 294 consecutive PHPT patients. Biochemical evaluation included total and ionized serum calcium, phosphate, creatinine, immunoreactive intact PTH, and 25-hydroxyvitamin D3 levels in the fasting state. GFR was assessed with the Modification of Diet in Renal Disease Study formula. Results: The mean GFR of the whole group of PHPT patients was 92.3 ± 31.6 ml/min · 1.73 m2. The patients were divided into four groups according to National Kidney Foundation Disease Outcomes Quality Initiative (K/DOQI) guidelines: group 1 with normal or increased GRF (>90 ml/min · 1.73 m2; n = 153); group 2 with mild decreased GFR (60–89 ml/min · 1.73 m2; n = 90); group 3 with moderately decreased GFR (30–59 ml/min · 1.73 m2; n = 45); and group 4 with severely decreased GFR (<30 ml/min · 1.73 m2; n = 6). PTH levels were comparable across groups 1–3, whereas group 4 showed significantly higher PTH levels (P < 0.0001). Conclusion: In our series of PHPT patients, only a severe impairment of GFR was characterized by a further PTH increase. These findings challenge the concept of a PTH elevation below the threshold of 60 ml/min of GFR. In a large series of contemporary PHPT patients, only a severe impairment of glomerular filtration rate (i.e., <30 ml/min/1.73 m2) is characterized by a further PTH elevation.