Abstract
BackgroundVitamin D status and renal function are well-known independent predictors of serum parathyroid hormone (PTH) levels. We aimed to describe the combined effects of 25-hydroxy vitamin D (25(OH)D), glomerular filtration rate (GFR) and age on serum PTH levels across the whole clinical spectrum.MethodsWe retrieved from our endocrinology center database all PTH measurement between 2012 and 2020 for which a simultaneous measurement of serum 25(OH)D, calcium and creatinine was available. Age, sex and diagnosis were available for all subjects. Intact PTH was measured using the same electrochemiluminescence assay.ResultsThere were 6,444 adults and 701 children without a diagnosis of hyper- or hypoparathyroidism or abnormal serum calcium levels. In adults with 25(OH)D≥12 ng/mL multiple regression models showed that serum PTH was negatively correlated with both 25(OH)D and GFR. Regression (-0.68 and -1.59 vs. -0.45 and -0.22 respectively), partial correlation (-0.16 and -0.35 vs. -0.12 and -0.10 respectively) and determination coefficients (0.14 vs. 0.031) were higher in CKD than in normal renal function. In subjects with 25(OH)D<12 ng/mL, GFR was the only significant predictor in those with CKD (β-coefficient=-2.5, r=-0.55) and 25(OH)D was the only significant predictor in those with normal renal function (β-coefficient=-2.05, r=-0.11). Increasing age was associated with higher PTH levels only in those with normal renal function and 25(OH)D≥12 ng/mL.ConclusionsWe showed that declining vitamin D and renal function have additive effects on serum PTH in subjects without vitamin D deficiency. In vitamin D deficient subjects this dependency is stronger but is not additive anymore.
Highlights
Vitamin D is a well-known predictor of serum parathyroid hormone (PTH) levels (1)
Age was showed to be positively associated with higher PTH levels, independently of vitamin D status (2, 14), but this is probably due to declining renal function with age
PTH rose with decreasing glomerular filtration rate (GFR) independently of vitamin D status (Figure 1)
Summary
Numerous studies, including very large samples (2), showed an inverse relation between serum 25hydroxy vitamin D (25(OH)D) and PTH levels, with a 25(OH)D breakpoint around 10 ng/mL below which the PTH levels rise sharply (3). Based on these data, the current guidelines proposed a cut-off value of 10 to 20 ng/mL for vitamin D deficiency (4–6) and [20-30] ng/mL for vitamin D insufficiency (4, 7). Vitamin D status and renal function are well-known independent predictors of serum parathyroid hormone (PTH) levels. We aimed to describe the combined effects of 25-hydroxy vitamin D (25(OH)D), glomerular filtration rate (GFR) and age on serum PTH levels across the whole clinical spectrum
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