Department of Nephrology, Osaka Saiseikai Nakatsu Hospital, Shibata, Kita-ku, Osaka, 530-0012, Japan.
Clin Exp Nephrol. 2010 Jun;14(3):233-8. doi: 10.1007/s10157-010-0264-5. Epub 2010 Feb 4.
Secondary hyperparathyroidism is one of the critical complications of end-stage renal disease patients. Conventionally intact parathyroid hormone (iPTH) was used to assess secondary hyperparathyroidism, but this assay measures both PTH(1-84) (full-length parathyroid hormone) and PTH(7-84) (amino (N)-terminal-cleaved parathyroid hormone). PTH(7-84) is biologically inactive or antagonistic for PTH. In this study, we examined the relationship between serum calcium concentration and PTH(7-84)/PTH(1-84) ratio and the effect of calcimimetics on the ratio in hemodialysis (HD) patients.
Ionized-calcium (iCa), iPTH, and whole PTH (wPTH) were measured at the start of HD sessions on HD patients. Patients were divided into four groups by presence (+) or absence (-) of vitamin D (VD) and calcimimetics (CM).
PTH(7-84)/PTH(1-84) ratios of the four groups [VD(-)CM(-), VD(+)CM(-), VD(-)CM(+) and VD(+)CM(+)] were 0.735, 0.799, 0.844, and 1.156, respectively. In VD(-)CM(-) and VD(+)CM(-) groups, iCa and PTH(7-84)/PTH(1-84) ratio showed equilateral correlation (r = 0.634, p < 0.001 and r = 0.360, p < 0.01, respectively). In calcimimetics-treated group, iCa and PTH(7-84)/PTH(1-84) ratio did not show correlation.
Whereas in the absence of calcimimetics cleavage of N-terminal PTH was regulated by serum calcium concentration, this regulation was abolished in the presence of calcimimetics. This suggests that cleavage of N-terminal PTH is regulated by calcium concentration via a calcium-sensing receptor and that calcimimetics may have a novel effect to reduce PTH level.
继发性甲状旁腺功能亢进症是终末期肾病患者的严重并发症之一。传统的完整甲状旁腺激素（iPTH）用于评估继发性甲状旁腺功能亢进症，但该检测方法同时测量 PTH(1-84)（全长甲状旁腺激素）和 PTH(7-84)（氨基（N）-末端切割甲状旁腺激素）。PTH(7-84) 对 PTH 无生物活性或具有拮抗作用。在这项研究中，我们研究了血清钙浓度与 PTH(7-84)/PTH(1-84) 比值之间的关系，并研究了钙敏剂对血液透析（HD）患者比值的影响。
在 HD 患者的 HD 治疗开始时测量离子钙（iCa）、iPTH 和全 PTH（wPTH）。根据是否存在维生素 D（VD）和钙敏剂（CM）将患者分为四组。
四组患者的 PTH(7-84)/PTH(1-84) 比值[VD(-)CM(-)、VD(+)CM(-)、VD(-)CM(+) 和 VD(+)CM(+)]分别为 0.735、0.799、0.844 和 1.156。在 VD(-)CM(-)和 VD(+)CM(-)组中，iCa 和 PTH(7-84)/PTH(1-84) 比值呈等边相关（r = 0.634，p < 0.001 和 r = 0.360，p < 0.01）。在钙敏剂治疗组中，iCa 和 PTH(7-84)/PTH(1-84) 比值无相关性。
在没有钙敏剂的情况下，N 端 PTH 的切割受血清钙浓度调节，而在有钙敏剂的情况下，这种调节被消除。这表明 N 端 PTH 的切割通过钙敏受体受钙浓度调节，钙敏剂可能具有降低 PTH 水平的新作用。
