Classification of Vitamin D status based on its metabolism

Our Fibroblast Growth Factor-23 (FGF-23) C-terminal ELISA assay was highlighted in a recent clinical study in hypertensive patients. The researchers evaluated whether individuals with “functional vitamin D deficiency” significantly benefit from vitamin D supplementation. As of now, there is no widely accepted definition of functional vitamin D deficiency. Thus, the authors explored the hypothesis that a specific definition of functional vitamin D deficiency could help identify individuals who would significantly benefit from vitamin D supplementation.

The authors concluded that the criteria for functional vitamin D deficiency indicate that patients with vitamin D deficiency do not experience significant improvements in bone markers or cardiovascular risk factors following vitamin D supplementation. Furthermore, additional research is needed to determine whether measuring vitamin D metabolites alongside 25(OH)D is beneficial for accurately classifying vitamin D status and identifying individuals who would particularly benefit from vitamin D treatment.

Classification of Vitamin D status based on its metabolism

Classification of Vitamin D Status Based on Vitamin D Metabolism: A Randomized Controlled Trial in Hypertensive Patients. Zelzer S, Meinitzer A, Enko D, Keppel MH, Herrmann M, Theiler-Schwetz V, Trummer C, Schmitt L, Tomaschitz A, Sadoghi P, Dierkes J, Pludowski P, Zittermann A, März W, Pilz S. Nutrients. 2024 Mar 14;16(6):839. doi: 10.3390/nu16060839. PMID: 38542750; PMCID: PMC10975656.

Abstract

Circulating 25-hydroxyvitamin D (25(OH)D) is the generally accepted indicator of vitamin D status. Since hydroxylation of 25(OH)D to 24-25-dihydroxyvitamin D (24,25(OH)2D) is the first step of its catabolism, it has been suggested that a low 24,25(OH)D level and a low vitamin D metabolite ratio (VMR), i.e., 24,25(OH)2D divided by 25(OH)D, may indicate high vitamin D requirements and provide additional diagnostic information beyond serum 25(OH)D. We, therefore, evaluated whether the classification of “functional vitamin D deficiency”, i.e., 25(OH)D below 50 nmol/L, 24,25(OH)2D below 3 nmol/L and a VMR of less than 4%, identifies individuals who benefit from vitamin D supplementation. In participants of the Styrian Vitamin D Hypertension trial, a randomized controlled trial (RCT) in 200 hypertensive patients with serum 25(OH)D below 75 nmol/L, who received either 2.800 international units of vitamin D per day or placebo over 8 weeks, 51 participants had functional vitamin D deficiency. In these individuals, there was no treatment effect of vitamin D supplementation on various parameters of bone metabolism and cardiovascular risk except for a significant effect on parathyroid hormone (PTH) and expected changes in vitamin D metabolites. In conclusion, a low vitamin D metabolite profile did not identify individuals who significantly benefit from vitamin D supplementation with regard to bone markers and cardiovascular risk factors. The clinical significance of functional vitamin D deficiency requires further evaluation in large vitamin D RCTs.

BIOMEDICA provides two distinct ELISA assays to reliably quantify FGF23 concentrations in human serum and plasma.

 FGF23 intact ELISA (cat. no. BI-20700)

 FGF23 (C-terminal) ELISA (cat. no. BI-20702)

Features and benefits  

• MULTI-MATRIX: for plasma, serum, cell-culture

• CONVENIENT: 50 µl sample/well, all buffers included

• RELIABLE: validated following quality guidelines

• COMPARABLE: good correlation with existing kits

• EASY HANDLING: 7 prediluted standards, 2 controls

• TRUSTED: cited in more than 80 publications

All Assays are Developed & Manufactured by Biomedica