Phelps Kenneth R, Mason Darius L
Clin Nephrol. 2020 Aug;94(2):70-77. doi: 10.5414/CN110043.
Seven theories address the evolution of secondary hyperparathyroidism (SHPT) as chronic kidney disease (CKD) progresses. The tradeoff-in-the-nephron hypothesis states that the plasma parathyroid hormone ([PTH]) concentration rises because an increased phosphate concentration in the cortical distal nephron ([P]) reduces the ionized calcium concentration in that segment. In the present study, we compared this hypothesis to its predecessors.
We studied 30 patients with estimated glomerular filtration rate (eGFR) less than 60 mL/min/1.73m (mean 29.5). To examine historic theories, we performed regressions of [PTH] on plasma concentrations of ionized calcium, phosphorus, 1,25-dihydroxyvitamin D, 25-hydroxyvitamin D, and fibroblast growth factor 23, and on calcium excreted per volume of filtrate (E/C). To assess the tradeoff-in-the-nephron hypothesis, we examined regressions of [PTH] on 100/eGFR and phosphorus excreted per volume of filtrate (E/C).
Regressions pertinent to historic theories yielded significant direct relationships between [PTH] and both E/C and [FGF23], but neither association supported the theory to which it pertained. [PTH] varied directly with 100/eGFR and with E/C, a surrogate for [P]. E/C correlated strongly with 100/eGFR.
The only theory of SHPT that our data support is the tradeoff-in-the-nephron hypothesis. Other theories are not supported.
有七种理论阐述了随着慢性肾脏病（CKD）进展，继发性甲状旁腺功能亢进（SHPT）的演变过程。肾单位权衡假说认为，血浆甲状旁腺激素（[PTH]）浓度升高是因为皮质远端肾单位中磷酸盐浓度（[P]）增加，降低了该节段的离子钙浓度。在本研究中，我们将这一假说与其之前的理论进行了比较。
我们研究了30例估计肾小球滤过率（eGFR）低于60 mL/min/1.73m²（平均29.5）的患者。为检验既往理论，我们对[PTH]与血浆离子钙、磷、1,25-二羟维生素D、25-羟维生素D、成纤维细胞生长因子23的浓度，以及每单位滤液中排出的钙（E/C）进行了回归分析。为评估肾单位权衡假说，我们对[PTH]与100/eGFR以及每单位滤液中排出的磷（E/C）进行了回归分析。
与既往理论相关的回归分析显示，[PTH]与E/C和[FGF23]均呈显著正相关，但这两种关联均不支持其所属的理论。[PTH]与100/eGFR以及作为[P]替代指标的E/C直接相关。E/C与100/eGFR密切相关。
我们的数据支持的SHPT唯一理论是肾单位权衡假说。其他理论未得到支持。
