Colussi G, Macaluso M, Brunati C, Minetti L
Division of Nephrology and Dialysis, Niguarda-Cà Granda Hospital, Milan, Italy.
Miner Electrolyte Metab. 1994;20(5):294-301.
In 10 adult patients (5 females and 5 males, aged 13-57 years) with Gitelman's syndrome (GS, or hypocalciuric variant of Bartter's syndrome, characterized by chronic renal hypokalemia, metabolic alkalosis, hypomagnesemia and hypocalciuria), parameters of Ca metabolism and calciotropic hormone levels were evaluated. Hypocalciuria was associated with a marked reduction of fractional excretion of ionized Ca (as compared with 16 sex- and age-matched controls) and normal filtered Ca load, as indicated by serum ionized Ca; hypocalciuria was thus the result of increased tubular reapsorption of filtered Ca. Plasma levels of total Ca were increased in GS (p < 0.02) but ionized Ca was not different from controls; percent fraction of ionized to total Ca was reduced, indicating increased Ca complexation and/or protein binding, possibly related to a metabolic alkalosis-induced increase of plasma albumin affinity for Ca. Levels of plasma total protein and albumin were similar in GS and controls. Despite similar ionized Ca levels, PTH1-84 was lower in GS than in controls, indicating abnormal ionized Ca-PTH relationship, possibly related to hypomagnesemia. Plasma 1,25(OH)2D levels were not different in GS and in controls, and intestinal fractional Ca absorption (evaluated with a simplified method using stable Sr as a tracer) was not reduced in 4 patients. However, in 5 patients bone mineral density in the forearm (3 patients) or lumbar spine (2 patient) was normal. Thus, despite chronic hypocalciuria and normal 1,25(OH)2D levels, Ca 'thesaurosis' does not occur in bones of GS patients; a likely explanation is that, despite normal 'fractional' intestinal Ca absorption, 'net' intestinal absorption is reduced, due to increased intestinal Ca secretion.
对10例患有吉特曼综合征（GS，或巴特综合征的低钙尿变异型，其特征为慢性肾性低钾血症、代谢性碱中毒、低镁血症和低钙尿症）的成年患者（5名女性和5名男性，年龄13 - 57岁）评估了钙代谢参数和钙调节激素水平。低钙尿症与离子钙分数排泄显著降低相关（与16名性别和年龄匹配的对照相比），且血清离子钙表明滤过钙负荷正常；因此，低钙尿症是肾小管对滤过钙重吸收增加的结果。GS患者血浆总钙水平升高（p < 0.02），但离子钙与对照无差异；离子钙占总钙的百分比降低，表明钙络合和/或蛋白质结合增加，这可能与代谢性碱中毒导致血浆白蛋白对钙的亲和力增加有关。GS患者和对照的血浆总蛋白和白蛋白水平相似。尽管离子钙水平相似，但GS患者的PTH1 - 84低于对照，表明离子钙 - PTH关系异常，可能与低镁血症有关。GS患者和对照的血浆1,25(OH)2D水平无差异，并且4例患者的肠道钙分数吸收（用使用稳定锶作为示踪剂的简化方法评估）未降低。然而，5例患者中，前臂（3例患者）或腰椎（2例患者）的骨密度正常。因此，尽管存在慢性低钙尿症且1,25(OH)2D水平正常，但GS患者的骨骼中并未发生钙“蓄积”；一个可能的解释是，尽管肠道钙“分数”吸收正常，但由于肠道钙分泌增加，肠道“净”吸收减少。
