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Editorial
. 2018 Apr 6;13(4):524-526.
doi: 10.2215/CJN.01730218. Epub 2018 Mar 5.

Clear the Fog around Parathyroid Hormone Assays: What Do iPTH Assays Really Measure?

Berthold Hocher  1   2   3 , Shufei Zeng  1   4
Affiliations
Editorial

Clear the Fog around Parathyroid Hormone Assays: What Do iPTH Assays Really Measure?

Berthold Hocher et al. Clin J Am Soc Nephrol. .
No abstract available

Keywords: Assays; Biological Assay; CKD; PTH; oxidative stress.

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Figures

Figure 1.
Figure 1.
First to third generation parathyroid hormone (PTH) assays target different regions of the secreted PTH molecule and ignore PTH oxidation at Met8 and Met18. (A) The first generation of PTH assays typically uses just one antibody directed toward the midregion of the PTH1–84 sequence and detects a mixture of mature PTH1–84, bioinactive C-terminal fragments, and N-terminal PTH fragments. The second generation PTH assays (also called intact PTH assays) are two-site immunoassays and typically have a solid-phase capture antibody directed toward the C-terminal region of PTH (amino acids 26–32 or 39–84) and a detection antibody directed toward the N terminus (usually toward amino acids 12–24). In third generation PTH assays, the detection antibody epitope was targeted to amino acids 1–4. The solid-phase capture antibodies directed toward the C-terminal region of PTH were the same as for second generation PTH assays. Methionine residues that might be oxidized are marked with red triangles. (B) Amino acids, such as methionine, at positions 8 and 18 (red triangles in A) can be oxidized under conditions of oxidative stress. The first oxidation step is reversible, whereas the second one is not. (C) Amino acids 8 and 18 in the PTH molecule are belonging to the PTH receptor binding site of the hormone. An oxidation of these methionone residues alters the hormone receptor interaction. The nowadays used second and third generation PTH assays cannot distinguish between oxidized and nonoxidized PTH1–84 and/or N-terminal oxidized and nonoxidized PTH fragments.
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