KDIGO CATEGORIES OF GLOMERULAR FILTRATION RATE AND PARATHYROID HORMONE SECRETION IN PRIMARY HYPERPARATHYROIDISM

The recent Fourth Workshop on the Management of Asymptomatic primary hyperparathyroidism (PHPT) maintained the threshold of 60 mL/min for decreased renal function, below which surgery is recommended. This study investigated the relationship between different stages of renal insufficiency and parathyroid hormone (PTH) levels in an updated case series of PHPT patients.

This was a retrospective, cross-sectional study involving 379 consecutive PHPT patients. Biochemical evaluation included total and ionized serum calcium, phosphate, creatinine, immunoreactive intact PTH, and 25-hydroxyvitamin D3 (25[OH]D3) levels in the fasting state. Glomerular filtration rate (GFR) was estimated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation.

Mean CKD-EPI estimated GFR was 81.9 ± 20.3 mL/min/1.73 m(2), and median GFR was 84.0 mL/min/1.73 m(2) (interquartile range, 26.8 mL/min/1.73 m(2)). The patients were divided into 5 groups according to the Kidney Disease: Improving Global Outcomes 2012 guidelines: group 1 with normal or increased GFR (>90 mL/min/1.73 m(2)); group 2 with mild GFR decrease (60 to 89 mL/min/1.73 m(2)); group 3a with mild to moderate GFR decrease (45 to 59 mL/min/1.73 m(2)); group 3b with moderate to severe GFR decrease (30 to 44 mL/min/1.73 m(2)); and group 4 with severe GFR decrease (<30 mL/min/1.73 m(2)). Among the 5 groups of patients, serum calcium levels were different (P = .025), whereas 25(OH)D3 levels were not (P = .36). PTH levels were comparable across groups 1 through 3a, but they were significantly higher in groups 3b and 4 (P<.0001).

In our series of PHPT patients, PTH levels did not rise as a result of renal impairment until GFR decreased below 45 mL/min/1.73 m(2).