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Hypocalciuria in Patients with Gitelman’s Syndrome:
Role of Hypomagnesemia
Chun-Chi Chen*, Hsin-Chi Wu**, Yu-Juei Hsu*, Chih-Jen Cheng*, Sung-Sen Yang*,
Pauling Chu* and Shih-Hua Lin*
*Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National
Defense Medical Center, Taipei, Taiwan
**Division of Nephrology, Ten-Chen General Hospital (Yang-Mei), Tao-Yuan, Taiwan
Abbreviated title: Mechanism of hypocalciuria in Gitelman’s Syndrome
Keywords: Gitelman’s syndrome, hypocalciuria, hypomagnesemia, hypovolemia.
Address all correspondence to:
Shih-Hua Lin, MD
Division of Nephrology, Department of Medicine
Tri-Service General Hospital
No 325, Section 2, Cheng-Kung Road,
Neihu 114, Taipei, Taiwan
Tel: 886-2-87927213
Fax: 886-2-87927134
E-mail: [email protected]
1
吉特曼氏症候群病人之低尿鈣：低血鎂的角色
陳俊吉*、吳欣吉**、許育瑞*、鄭智仁*、楊松昇*、朱柏齡*、林石化*
*三軍總醫院內科部腎臟內科
**楊梅天成醫院腎臟內科
關鍵詞：吉特曼氏症候群、低尿鈣、低血鎂、低血容積
通訊作者：
林石化教授
台北市 114 內湖區成功路二段 325 號 三軍總醫院內科部腎臟內科
電話：(02) 87927213
傳真：(02) 87927134
E-mail: [email protected]
2
中文摘要
背景：低尿鈣及低血鎂，是吉特曼氏症候群病人的兩個典型臨床表徵。在某些人類低血
鎂疾病狀態，雖保有正常的腎臟髓質功能，但亦合併有低尿鈣的現象；這顯示低血鎂和
低尿鈣可能存有相互影響的關係。
目的：我們主要探討低血鎂在吉特曼氏症候群病人之低尿鈣所扮演的角色。
方法：十二位確診為鈉氯離子運輸蛋白（NCC）基因突變的吉特曼氏症候群病人參與本
試驗，我們使其接受短時間靜脈輸注（硫酸鎂，每公斤 0.35 mmol，一小時）及較長時
間口服（氧化鎂，每日 37 mmol，四週）補充鎂離子，並收集血液及尿液檢體，以檢測
電解質、生化及相關荷爾蒙之變化。另外，十二位經年齡及性別配對的健康的志願者作
為對照組比較。
結果：與健康志願者比較，吉特曼氏症候群病人有顯著的低尿鈣（鈣離子濾過分率為 0.15
± 0.03 vs. 1.49 ± 0.23%, p < 0.05；每日尿鈣總排泄量為 4.2 ± 1.6 vs. 50.4 ± 10.8 mmol, p <
0.05）
、低血鎂（0.52 ± 0.1 vs. 0.85 ± 0.1 mmol/L, p < 0.05）及副甲狀腺功能低下（4.6 ± 2.1
vs. 34.1 ± 8.6 ng/L, p < 0.05）之臨床表徵。經短時間靜脈輸注硫酸鎂後，會顯著提升鈣
離子尿排泄量（鈣/鈉濾過分率比 FECa/FENa 為 0.19 ± 0.11 至 3.42 ± 2.37, p < 0.05）及血
中副甲狀腺素濃度（4.6 ± 2.1 至 16.3 ± 5.3 ng/L, p < 0.05）。經較長時間口服氧化鎂補充
後，雖明顯提升血鎂及副甲狀腺素濃度，但鈣離子尿排泄量則無顯著提升；此外，有四
個病人雖然血鎂濃度已矯正回一般值，但卻仍持續存有低尿鈣現象。
結論：低血鎂本身並無法完全解釋吉特曼氏症候群病人之低尿鈣的發生，其它病生理機
轉仍需更進一步闡明，以瞭解其腎臟對於鈣及鎂離子之調控。
3
Abstract
Background: Hypocalciuria and hypomagnesemia are two characteristic findings in patients
with Gitelman’s syndrome (GS). Several hypomagnesemic states with intact renal medulla in
humans also have hypocalciuria, suggesting the association of hypomagnesemia with
hypocalciuria.
Aim: We evaluate the role of hypomagnesemia on hypocalciuria in human GS.
Methods: Twelve GS patients with thiazide-sensitive sodium-chloride cotransporter (NCC)
mutations received acute magnesium sulfate (MgSO4 0.35 mmol/kg) for one hour and chronic
oral magnesium oxide (MgO 37 mmol daily) for four weeks. Urine and blood were obtained
for the determination of electrolytes, biochemistries and hormones. Twelve age- and
sex-matched healthy normotensive volunteers were selected as controls.
Results: Compared with health subjects, GS patients had a severe hypocalciuria (FECa 0.15 ±
0.03 vs. 1.49 ± 0.23%, p < 0.05; daily urinary Ca2+ excretion 4.2 ± 1.6 vs. 50.4 ± 10.8 mmol, p
< 0.05), hypomagnesemia (0.52 ± 0.1 vs. 0.85 ± 0.1 mmol/L, p < 0.05) and low intact
parathyroid hormone (iPTH) (4.6 ± 2.1 vs. 34.1 ± 8.6 ng/L, p < 0.05). Acute MgSO4 infusion
remarkably increased urinary Ca2+ excretion (FECa/FENa, 0.19 ± 0.11 to 3.42 ± 2.37, p < 0.05)
and serum iPTH levels (4.6 ± 2.1 to 16.3 ± 5.3 ng/L, p < 0.05). Chronic MgO
supplementation significantly raised serum Mg2+ and i-PTH level but not urinary Ca2+
excretion. Furthermore, four patients who reached normal serum Mg2+ level after chronic
Mg2+ repletion had persistent hypocalciuria.
Conclusion: Hypomagnesemia alone cannot explain the pathogenesis of hypocalciuria in
patients with GS completely. Other mechanisms are still worthy to explore to understand the
renal Ca2+ and Mg2+ handling in GS patients.
4
Introduction
Gitelman’s syndrome (GS) (OMIM 263800), an inherited renal disorder, caused by
inactivating mutations in the SLC12A3 gene encoding the thiazide-sensitive sodium
(Na+)-chloride (Cl-) cotransporter (NCC) in distal convoluted tubule (DCT) and the clinical
manifestations of GS patients resemble those treated with chronic administration of thiazide
diuretics.1-3 Impaired NCC function in GS patients resulting in an increase of Na+ delivery to
collecting tubule (CT) leads to hypokalemic alkalosis by enhancing potassium (K+) and
hydrogen (H+) excretion for a counterbalance to increased Na+ reabsorption in CT.3,4 In
addition to hypokalemic alkalosis, hypomagnesemia and low urinary calcium (Ca2+) excretion
are characteristic biochemical features of GS.4-6 Although hypocalciuria has been widely used
to discriminate patients with GS from those with Bartter’s syndrome (BS) and other renal K+
wasting disorders clinically,7,8 the mechanisms responsible for hypocalciuria in patients with
GS remained a puzzle.
Previously, several studies in rats or mice treated with thiazides demonstrated that
volume contraction after thiazide administration contributed to augment passive Ca2+
reabsorption in proximal tubule (PT) may be the main cause for the development of
hypocalciuria.9-12 Furthermore, thiazide-treated NCC-null mice showed decreased fractional
delivery of Ca2+ in PT, but unaffected in DCT further supported the role of volume status in
the development of hypocalciuria in GS patients.13 However, injection of thiazide in the left
5
renal artery of dogs only affected Ca2+ excretion in the same-side kidney, even though volume
depletion may have influence on both kidneys.14 Moreover, acute treatment of low-dose
thiazide resulted in an enhanced expression of epithelial Ca2+ channels in DCT suggested
thiazide possibly cause hypocalciuria through regulation of Ca2+ reabsorption in DCT
directly.12 Recently, we have shown that acute volume repletion with normal saline in patients
with GS did not normalized urinary Ca2+ excretion, suggesting hypovolemia is not the sole
cause of hypocalciuria in GS.15
Although divalent mineral cations Ca2+ and magnesium (Mg2+) play diverse roles in
cellular physiological functions, the metabolism of Ca2+ and Mg2+ are closely linked.16
Experimental Mg2+ deficiency developed hypocalciuria after fed with Mg2+-depletion diet and
the responsiveness to calciotropic hormone was blunted.17,18 Some human hypomagnesemic
disorders, such as hereditary primary hypomagnesemia due to a mutation in the gamma
subunit of the Na+-K+-ATPase in the DCT, are also presented with hypocalciuria.19 These
findings suggested that hypomagnesemia might be involved in the regulation of urinary Ca2+
excretion. In patients with GS, hypomagnesemia usually coincide with hypocalciuria further
supported this possibility,20 but the relationship between hypomagnesaemia and hypocalciuria
is still not conclusively identified. In this study, we investigated the impact of
hypomagnesemia on the development of hypocalciuria to shed some light in the
understanding of the regulation of urinary Ca2+ excretion in GS patients.
6
Patients and Methods
Patients
This study protocol was approved by the Ethics Committee on Human Studies at
Tri-Service General Hospital, National Defense Medical Center, in Taiwan, R.O.C. All
subjects gave written informed consent before participating in this study.
We have collected twelve patients with GS (eleven males, one female, aged 19-40,
median 28 years old). The clinical diagnosis of GS have been established by criteria including
persistent hypokalemia (< 3.5 mmol/L) associated with renal K+ wasting (transtubular
potassium gradient, TTKG > 3), hypomagnesemia (< 0.7 mmol/L) with renal magnesium
(Mg2+) wasting (the molar ratio of urinary Mg2+ to creatinine > 0.14) and hypocalciuria (the
molar ratio of urinary Ca2+ to creatinine < 0.1). All of these GS patients had SLC12A3
mutations, including 4 patients carrying homozygous mutation (T60M for 1, H90Y for 1,
IVS13 -191C→T for 2), 7 patients with compound heterozygous mutations (T60M/R642C,
T60M/2881-2delAG, T163M/N426K, T163M/S710X, T163M/W844X, R871H/2881-2delAG,
S710X/2881-2delAG) and 1 patient having triple mutations (T163M/R871H/IVS21 +253 C→
T ).15,21 They received only regular K+ and Mg2+ supplementation without other medications.
Mg2+ supplement was discontinued at least four weeks prior to the investigation. Twelve
healthy normotensive volunteers, comparable in sex, age, and body mass index comprised the
control group. Their physical and biochemistry examinations were normal. All of the GS
7
patients and healthy subjects (HS) maintained on an unrestricted regular balanced diet. Acute
Mg2+ infusion and chronic Mg2+ supplementation were conducted after collection of baseline
fasting samples in three different time frames, which were separated by 2-week interval.
Methods
Baseline renal function & biochemistries
Twenty four-hour urine samples before Mg2+ administration were collected from all of
the GS patients and HS for estimating their baseline renal function and daily urine Ca2+ and
Mg2+ excretion. After twelve-hour fasting, the subjects voided and drank 200 ml of tap water
at 08:00AM. A timed serum and urine collection at 09:00AM was obtained for the
determination of the fasting serum hemoglobin, albumin, electrolytes, intact parathyroid
hormone (iPTH), plasma renin activity, aldosterone and urinary electrolytes. Two 20-gauge
Teflon catheters were placed percutaneously into antecubital veins of GS patients. One
catheter is for MgSO4 infusion and another one is for blood sampling.
Acute Mg2+ infusion
Magnesium sulfate (MgSO4 10% solution, 0.35 mmol/kg) was infused slowly via a
controlled pump over one hour since 09:00AM to raise serum Mg2+ concentration. Spot urine
and blood samples were collected hourly in the first four-hour interval and at the next
09:00AM.
Chronic Mg2+ supplementation
Two weeks apart from the acute Mg2+ repletion with 12-hour fasting, all GS patients
8
received oral magnesium oxide (MgO) 1500 mg (37 mmol Mg2+) daily in 3-4 divided doses
for four weeks, adapted from the supplemental protocol from Bettinelli et al.7 Two of all
patients were treated with a decreased dosage of 250 mg three or four times daily because of
the development of diarrhea. Fasting spot urine and blood samples were collected after
four-week Mg2+ repletion.
Analytical methods
Biochemistries: All measurements were performed in duplicate. Venous H+ and bicarbonate
(by an ABL 510, Radiometer, Copenhagen, Denmark), and serum ionized Ca2+ concentration
were measured immediately after blood collection. The remaining samples were immediately
stored at -40℃ for determination of Na+, K+, Cl-, creatinine (Cr), blood urea nitrogen (BUN),
total Ca2+, Mg2+ and osmolality in serum and urine by automated methods (AU 5000
chemistry analyzer; Olympus, Tokyo, Japan).
Hormones: Intact-PTH (iPTH) concentration was measured by radioimmunoassay (RIA)
using the intact PTH-Parathyroid Hormone Immunoassay kit (Nichols Institute Diagnostics,
San Juan Capistrano, CA, USA). Supine plasma renin activity was measured by
radioimmunoassay (RIA) using a kit (Diagnostic Product Corp, Llamberis, UK). Serum
aldosterone concentration was measured by the two-antibody RIA method with a SPAC-S
aldosterone kit (Daiichi Radioisotope Institute, Tokyo, Japan).
9
Calculations
Urinary Ca2+ variations could be due to glomerular filtration rate (GFR) variations
affecting the Ca2+ filtered loads. We factored urinary Ca2+ excretion values by GFR (the
fractional excretion of Ca2+, FECa; the molar urinary Ca2+/Cr ratio, UCa/UCr) in order to assess
the tubular Ca2+ reclamations independently of GFR values in chronic Mg2+ supplementation.
The fractional excretion of Ca2+ and Na+ ratio (FECa/FENa) was used to discriminate between
selective effects on tubular Ca2+ reclamation that dissociate Ca2+ and Na+ excretion and
nonselective effects similarly affecting Ca2+ and Na+ reabsorption in acute Mg2+ infusion.22
Statistics
All data were expressed as mean ± standard deviation. One-way repeated measures
ANOVA was used for the data in acute Mg2+ infusion. Two-tail paired t test was analyzed for
the data in chronic Mg2+ supplement. A p value below 0.05 was considered statistically
significant.
10
Results
Characteristics in GS
As shown in Table 1, the GFR estimated by the creatinine clearance rate (CCr) did not
have remarkable change between GS and HS (102.0 ± 14.4 vs. 108.6 ± 15.0 mL/min). Serum
biochemistries and hormonal studies showed the patients presenting with the biochemical
features of GS, including hypokalemia (2.8 ± 0.3 vs. 4.3 ± 0.4 mmol/L, p < 0.05),
hypomagnesemia (0.52 ± 0.1 vs. 0.85 ± 0.1 mmol/L, p < 0.05), metabolic alkalosis (pH 7.44 ±
0.02 vs. 7.41 ± 0.01, p < 0.05), and slightly higher hemoglobin, serum albumin, and high
rennin activity (4.01 ± 2.52 vs. 0.45 ± 0.07 ng/L-s, p < 0.05) with high serum aldosterone
concentration (0.13 ± 0.04 vs. 0.08 ± 0.01 nmol/L, p < 0.05). Significantly lower serum iPTH
(4.6 ± 2.1 vs. 34.1 ± 8.6 ng/L, p < 0.05) but normal serum Ca2+ levels suggested that relative
hypoparathyroidism was observed in GS patients. Biochemistries of fasting spot urine
revealed the excessive renal wasting of Na+, K+ and Mg2+, extremely low urinary Ca2+
excretion (FECa 0.15 ± 0.03 vs. 1.49 ± 0.23 %, p < 0.05) and impaired renal concentrating
ability in GS patients (osmolality 773 ± 94 vs. 1014 ± 127 mOsm/kg．H2O, p < 0.05).
Acute Mg2+ infusion
The serum Mg2+ level reached 1.6 ± 0.1 mmol/L after one-hour MgSO4 infusion. In
parallel, the 3rd-hour serum total Ca2+ (2.3 ± 0.1 to 2.1 ± 0.1 mmol/L, p < 0.05) and ionized
11
Ca2+ levels (1.20 ± 0.05 to 1.10 ± 0.05 mmol/L, p < 0.05) didn’t elevate but slightly declined.
As the aspect of hormone studies, 3.5-fold increase of serum iPTH (4.6 ± 2.1 to 16.3 ± 5.3
ng/L, p < 0.05) and significant decrease of renin activity (4.0 ± 2.5 to 1.0 ± 0.6 ng/L-s, p <
0.05) and aldosterone (0.13 ± 0.04 to 0.08 ± 0.02, p < 0.05) concentration were noticed at the
3rd
hour.
The
response
of
PTH
can
be
explained
by
the
correction
of
hypomagnesemia-induced PTH suppression. The urinary Mg2+ excretion (FEMg/FENa) peaked
with 3-fold increase (3.85 ± 2.25 to 10.93 ± 4.89, p < 0.05) at the 3rd hour after MgSO4
infusion. The urinary Ca2+ excretion (FECa/FENa) had tremendous 18-fold increase (3.42 ±
2.37 vs. 0.19 ± 0.11, p < 0.001) at the second hour after MgSO4 infusion and the urinary Ca2+
excretion correlated with urinary Mg2+ excretion and serum Mg2+ concentration (p < 0.001)
(Figure 1).
Chronic Mg2+ supplementation
Table 2 revealed the laboratory data of GS patients after chronic magnesium
supplementation. After four-week MgO repletion, serum Mg2+ level significantly increased
(0.53 ± 0.06 to 0.67 ± 0.06 mmol/L, p < 0.05) along with an increased in serum iPTH
(5.9±0.9 to 9.1±2.8 ng/L). Although urinary Mg2+ excretion was increased by 1.6 folds,
urinary Ca2+ excretion was not significantly enhanced (FECa 0.13 ±0.03 to 0.15 ± 0.05 %).
Furthermore, four patients who reached normal serum Mg2+ level after chronic Mg2+
12
supplementation still had persistent hypocalciuria. Oral MgO 37 mmol daily for four weeks
did not cause any significant changes in body weight, blood pressure, heart rate, serum
creatinine and acid-base state. .
13
Discussion
In this study, we showed that all of our patients with GS have normal filtered load of
Ca2+ due to their normal baseline serum Ca2+ level and GFR. The remarkable hypocalciuria
indicated the presence of enhanced renal tubular Ca2+ reabsorption. The Mg2+
supplementation studies demonstrated that acute MgSO4 infusion corrected hypomagnesemia
and hypocalciuria and this calciuretic effect was strongly correlated with the serum Mg2+ level
and urinary Mg2+ excretion rate. However, chronic MgO repletion significantly increased the
serum Mg2+ level without simultaneous increase in urinary Ca2+ excretion.
The pathogenesis of hypocalciuria in GS is complex and not completely elucidated. The
majority (70%) of filtered Ca2+ reabsorption along the nephrons occurs via passive
paracellular Ca2+ reabsorption in the proximal tubules through passive diffusion and solvent
drag effect.23-25 Several animal studies suggested that enhanced Ca2+ reabsorption in PCT
secondary to hypovolemia resulting from loss of functions of NCC is responsible for the
hypocalciuria in GS.9-11,15 However, saline infusion restored the volume status in patients with
GS, which leaded to a significantly greater Na+ excretion rate, but there was only a small
increase in Ca2+ excretion rate. Furthermore, their urinary Ca2+ excretion rate was still much
less than that in control subjects before volume repletion.15 Thus, there might be other factors
participated in the development of hypocalciuria in patients with GS. Although there have
several hypotheses been proposed, including high transepithelial positive voltage by reduction
14
in NaCl reabsorption,26 compensatory hypertrophy of the downstream DCT with upregulation
of epithelial Ca2+ channels, transient receptor potential cation channel subfamily V, members
5 and 6 (TRPV5 and TRPV6),15 metabolic alkalosis27,28 or abnormal responsiveness to
calciotropic hormones,17,29,30 lack of strong evidences to support their roles for the
hypocalciuria in GS.
Hypomagnesemia, another distinct finding in GS, showed the potential effect on
hypocalciuria in some diseases with coexisted hypomagnesemia and hypocalciuria and
change in urinary Ca2+ excretion is directly proportional to the change in Mg2+ excretion.31,32
The proposed explanations about the magnesium-related calciuresis included suppressed
synthesis or release of PTH by elevated serum Mg2+ concentration29,30 and competitive Mg2+
reabsorption enhancing urinary Ca2+ loss.31,33,34 However, a recent study demonstrated Mg2+
infusion to rats significantly increased urinary Ca2+ excretion, whereas parathyroidectomy and
treatment with furosemide did not abolish this magnesium-induced hypercalciuria.35 These
data suggested that the effect may be PTH-independent and mediated by the distal nephron,
instead of the thick ascending limb. Furthermore, Ca2+ uptake by TRPV5 in Xenopus oocytes
was directly inhibited by Mg2+.36 These findings supported the hypothesis that urinary Mg2+
directly inhibits distal tubule-mediated renal Ca2+ reabsorption.
Consistent with animal studies, human experiments with brief Mg2+ infusion in different
populations including healthy subjects,36,37 pregnant women with preeclampsia32 or patients
15
with acute myocardial infarction all demonstrated with 3-20 folds increase of urinary Ca2+
excretion independent of GFR.38 Similarly, acute MgSO4 infusion in GS showed comparable
increment of urinary Ca2+ excretion (18 folds) in the present study. Thus, acute Mg2+
supplementation can interfere with the interpretation of urinary Ca2+ excretion. Mg2+
supplement should be discontinued when the urinary Ca2+ excretion is used to distinguish GS
from BS.
Clinically, patients with GS presented with life-long hypomagnesemia and hypocalciuria
rather than temporary disturbances of Mg2+ and Ca2+ metabolism. Thus, the effects of chronic
Mg2+ supplementation on urinary Ca2+ excretion in GS patients were also investigated.
Unlike acute Mg2+ infusion, we found the serum Mg2+ level can reached the subnormal level
(0.53 to 0.67 mmol/L) after chronic oral MgO supplementation but the urinary Ca2+ excretion
can not be enhanced significantly. Furthermore, those who reached normal serum Mg2+ level
(n = 4) after chronic Mg2+ supplementation still had persistent hypocalciuria. Contrary to two
case reports,39,40 our finding was similar to that in one prospective study showing that the
administration of magnesium pyrrolidone carboxylate (30 mmol daily) for four weeks
significantly increased the serum Mg2+ concentration (0.46 to 0.57 mmol/L) but failed to see a
significant increase in urinary Ca2+ excretion. Moreover, some GS patients with
normomagnesemia and concomitant hypocalciuria questioned the role of hypomagnesemia on
the development of hypocalciuria in GS.6,41
16
It has been shown that Mg2+ depletion in both humans and animals lead to the disturbed
bone and mineral metabolism and hypomagnesemia can impair the function of calciotropic
hormones.17 Reduced PTH concentration in GS patients with hypomagnesemia may suggest a
reduced skeletal sensitivity to PTH despite the fact that Mg2+ deficiency has a suppressive
effect on bone formation independently.18 Daily Mg2+ repletion has been shown to increase
bone mass in Mg2+-deficient osteoporotic women as well as the normal young adults.42,43
With an increase in serum Mg2+ concentration after chronic Mg2+ supplementation in GS
patients, a Ca2+ influx into bone may develop, followed by an increase of the Ca2+ bone
content through the enhanced serum PTH concentration and reduced bone resistance. This
response may also partly account for persistent hypocalciuria with chronic Mg2+
supplementation in GS.
The limitations of our study included small case numbers and lack of disease control
group. First, the low prevalence of GS makes the difficulty to accumulate large group of
patients. In addition, disease control with coexisted hypomagnesemia and hypocalciuria is
even more unusual and patients can not tolerate chronic Mg2+ supplementation on a larger
dosage very well.
In conclusion, acute Mg2+, but not chronic Mg2+ supplementation enhanced the urinary
Ca2+ excretion in patients with GS. The hypomagnesemia alone might not explain the
mechanisms responsible for the development of hypocalciuria completely in GS. Further
17
studies are warranted to explore the effects of chronic Mg2+ deficiency on urinary Ca2+
excretion in patients with GS.
18
References
1.
Mastroianni N, Bettinelli A, Bianchetti M, et al: Novel molecular variants of the Na-Cl
cotransporter gene are responsible for Gitelman syndrome. Am J Hum Genet 1996; 59:
1019-26.
2.
Simon DB and Lifton RP: The molecular basis of inherited hypokalemic alkalosis:
Bartter's and Gitelman's syndromes. Am J Physiol 1996; 271: F961-6.
3.
Simon DB, Nelson-Williams C, Bia MJ, et al: Gitelman's variant of Bartter's syndrome,
inherited hypokalaemic alkalosis, is caused by mutations in the thiazide-sensitive Na-Cl
cotransporter. Nat Genet 1996; 12: 24-30.
4.
Gitelman HJ, Graham JB and Welt LG: A familial disorder characterized by hypokalemia
and hypomagnesemia. Ann N Y Acad Sci 1969; 162: 856-64.
5.
Gitelman HJ, Graham JB and Welt LG: A new familial disorder characterized by
hypokalemia and hypomagnesemia. Trans Assoc Am Physicians 1996; 79: 221-35.
6.
Lin SH, Cheng NL, Hsu YJ and Halperin ML: Intrafamilial phenotype variability in
patients with Gitelman syndrome having the same mutations in their thiazide-sensitive
sodium/chloride cotransporter. Am J Kidney Dis 2004; 43: 304-12.
7.
Bettinelli A, Basilico E, Metta MG, Borella P, Jaeger P and Bianchetti MG: Magnesium
supplementation in Gitelman syndrome. Pediatr Nephrol 1999; 13: 311-4.
8.
Lin SH, Shiang JC, Huang CC, Yang SS, Hsu YJ and Cheng CJ: Phenotype and genotype
19
analysis in Chinese patients with Gitelman's syndrome. J Clin Endocrinol Metab 2005; 90:
2500-7.
9.
Breslau N, Moses AM and Weiner IM: The role of volume contraction in the
hypocalciuric action of chlorothiazide. Kidney Int 1976; 10: 164-70.
10. Nijenhuis T, Hoenderop JG, Loffing J, van der Kemp AW, van Os CH and Bindels RJ:
Thiazide-induced hypocalciuria is accompanied by a decreased expression of Ca2+ transport
proteins in kidney. Kidney Int 2003; 64: 555-64.
11. Nijenhuis T, Vallon V, van der Kemp AW, Loffing J, Hoenderop JG and Bindels RJ:
Enhanced passive Ca2+ reabsorption and reduced Mg2+ channel abundance explains
thiazide-induced hypocalciuria and hypomagnesemia. J Clin Invest2005; 115: 1651-8.
12. Lee CT, Shang S, Lai LW, Yong KC and Lien YH: Effect of thiazide on renal gene
expression of apical calcium channels and calbindins. Am J Physiol Renal Physiol 2004; 287:
F1164-70.
13. Loffing J, Vallon V, Loffing-Cueni D, et al.: Altered renal distal tubule structure and
renal Na(+) and Ca(2+) handling in a mouse model for Gitelman's syndrome. J Am Soc
Nephrol 2004; 15: 2276-88.
14. Costanzo LS and Weiner IM: On the hypocalciuric action of chlorothiazide. J Clin Invest
1974; 54: 628-37.
15. Cheng CJ, Shiang JC, Hsu YJ, Yang SS and Lin SH: Hypocalciuria in patients with
20
Gitelman syndrome: role of blood volume. Am J Kidney Dis 2007; 49: 693-700.
16. Hebert SC: Extracellular calcium-sensing receptor: implications for calcium and
magnesium handling in the kidney. Kidney Int 1996; 50: 2129-39.
17. Zofkova I and Kancheva RL: The relationship between magnesium and calciotropic
hormones. Magnes Res 1995; 8: 77-84.
18. Colussi G, Macaluso M, Brunati C and Minetti L: Calcium metabolism and calciotropic
hormone levels in Gitelman's syndrome. Miner Electrolyte Metab 1994; 20: 294-301.
19. Meij IC, Koenderink JB, van Bokhoven H, et al: Dominant isolated renal magnesium
loss is caused by misrouting of the Na(+),K(+)-ATPase gamma-subunit. Nat Genet 2000; 26:
265-6.
20. Naesens M, Steels P, Verberckmoes R, Vanrenterghem Y and Kuypers D: Bartter's and
Gitelman's syndromes: from gene to clinic. Nephron Physiol 2004; 96: 65-78.
21. Lo YF, Nozu K, Iijima K, et al: Recurrent Deep Intronic Mutations in the SLC12A3 Gene
Responsible for Gitelman's Syndrome. Clin J Am Soc Nephrol. 2010; 6(2).
22. Blanchard A, Jeunemaitre X, Coudol P, et al: Paracellin-1 is critical for magnesium and
calcium reabsorption in the human thick ascending limb of Henle. Kidney Int 2001; 59:
2206-15.
23. Bindels RJ: Calcium handling by the mammalian kidney. J Exp Biol 1993; 184: 89-104.
24. Hoenderop JG, Nilius B and Bindels RJ: Calcium absorption across epithelia. Physiol
21
Rev 2005; 85: 373-422.
25. Hoenderop JG, Willems PH and Bindels RJ: Toward a comprehensive molecular model
of active calcium reabsorption. Am J Physiol Renal Physiol 2000; 278: F352-60.
26. Friedman PA: Basal and hormone-activated calcium absorption in mouse renal thick
ascending limbs. Am J Physiol 1988; 254: F62-70.
27. Nijenhuis T, Renkema KY, Hoenderop JG and Bindels RJ: Acid-base status determines
the renal expression of Ca2+ and Mg2+ transport proteins. J Am Soc Nephrol 2006; 17:
617-26.
28. Sutton RA, Wong NL and Dirks JH: Effects of metabolic acidosis and alkalosis on
sodium and calcium transport in the dog kidney. Kidney Int 1979; 15: 520-33.
29. Takatsuki K, Hanley DA and Sherwood LM: Effects of magnesium ion on parathyroid
hormone secretion in vitro. Calcif Tissue Int 1980; 32: 201-6.
30. Sherwood LM, Herrman I and Bassett CA: Parathyroid hormone secretion in vitro:
regulation by calcium and magnesium ions. Nature 1970; 225: 1056-8.
31. Samiy AH, Brown JL and Globus DL: Effects of magnesium and calcium loading on
renal excretion of electrolytes in dogs. Am J Physiol 1960; 198: 595-8.
32. Samiy AH, Brown JL, Globus DL, Kessler RH and Thompson DD: Interrelation between
renal transport systems of magnesium and calcium. Am J Physiol 1960; 198: 599-602.
33. Cruikshank DP, Pitkin RM, Donnelly E and Reynolds WA: Urinary magnesium, calcium,
22
and phosphate excretion during magnesium sulfate infusion. Obstet Gynecol 1981; 58: 430-4.
34. Le Grimellec C, Roinel N and Morel F: Simultaneous Mg, Ca, P,K,Na and Cl analysis in
rat tubular fluid. II. During acute Mg plasma loading. Pflugers Arch 1973; 340: 197-210.
35. Bonny O, Rubin A, Huang CL, Frawley WH, Pak CY and Moe OW: Mechanism of
Urinary Calcium Regulation by Urinary Magnesium and pH. J Am Soc Nephrol, 2008; 19:
1530-7.
36. Chesley LC and Tepper I: Some effects of magnesium loading upon renal excretion of
magnesium and certain other electrolytes. J Clin Invest 1958; 37: 1362-72.
37. Massry SG, Ahumada JJ, Coburn JW and Kleeman CR: Effect of MgCl2 infusion on
urinary Ca and Na during reduction in their filtered loads. Am J Physiol 1970; 219: 881-5.
38. Rasmussen HS, Cintin C, Aurup P, Breum L and McNair P: The effect of intravenous
magnesium therapy on serum and urine levels of potassium, calcium, and sodium in patients
with ischemic heart disease, with and without acute myocardial infarction. Arch Intern Med
1988; 148: 1801-5.
39. Cho YJ, Park GT, Cho YJ and Kim HJ: Renal potassium wasting and hypocalciuria
ameliorated with magnesium repletion in Gitelman's syndrome. J Korean Med Sci 1997; 12:
157-9.
40. Pantanetti P, Arnaldi G, Balercia G, Mantero F and Giacchetti G: Severe
hypomagnesaemia-induced hypocalcaemia in a patient with Gitelman's syndrome. Clin
23
Endocrinol (Oxf) 2002; 56: 413-8.
41. Tosi F, Bianda ND, Truttmann AC, et al.: Normal plasma total magnesium in Gitelman
syndrome. Am J Med 2004; 116: 573-4.
42. Sojka JE and Weaver CM: Magnesium supplementation and osteoporosis. Nutr Rev 1995;
53: 71-4.
43. Dimai HP, Porta S, Wirnsberger G, et al: Daily oral magnesium supplementation
suppresses bone turnover in young adult males. J Clin Endocrinol Metab 1998; 83: 2742-8.
24
Table 1. Biochemical investigations in healthy controls (HS) and patients with
Gitelman’s syndrome (GS)
HS (n=12)
GS (n=12)
143.3 ± 1.9
138.7 ± 2.1*
Potasium (mmol/L)
4.3 ± 0.4
2.8 ± 0.3*
Chloride (mmol/L)
108.0 ± 1.1
100.7 ± 2.9*
Magnesium (mmol/L)
0.85 ± 0.1
0.52 ± 0.1*
Calcium, total (mmol/L)
2.4 ± 0.1
2.3 ± 0.1
Calcium, ionized (mmol/L)
1.18 ± 0.04
1.15 ± 0.03
Bicarbonate (mmol/L)
24.9 ± 1.1
28.0 ± 0.8*
Venous pH
7.41 ± 0.01
7.44 ± 0.02*
Urea nitrogen (mmol/L)
4.89 ± 0.38
4.62 ± 0.49
Creatinine (mmol/L)
0.08 ± 0.01
0.08 ± 0.02
Albumin (g/L)
47.0 ± 1.6
49.0 ± 1.2*
Hemoglobin (g/L)
151.0 ± 12
166.0 ± 17*
Plasma renin activity (ng/L-s)
0.45 ± 0.07
4.01 ± 2.52*
Aldosterone (nmol/L)
0.08 ± 0.01
0.13 ± 0.04*
Intact parathyroid hormone (ng/L)
34.1 ± 8.6
4.6 ± 2.1*
Sodium (mmol/L)
169.0 ± 32
151.0 ± 25
Potassium (mmol/L)
58.0 ± 15
58.0 ± 10
Chloride (mmol/L)
212.0 ± 35
154.0 ± 36*
Magnesium (mmol/L)
3.2 ± 1.1
2.1 ± 0.7
Calcium (mmol/L)
4.0 ± 1.1
0.2 ± 0.1*
Creatinine (mmol/L)
18.4 ± 4.7
13.3 ± 1.7*
Osmolality (mOsm/kg．H2O)
1014 ± 127
773 ± 94*
Creatinine Clearance (mL/min)
108.6 ± 15.0
102.0 ± 14.4
FENa (%)
0.54 ± 0.21
0.63 ± 0.13
FEK (%)
6.3 ± 2.7
11.8 ± 3.5*
FEMg (%)
1.70 ± 0.56
2.39 ± 0.96*
FECa (%)
1.49 ± 0.23
0.15 ± 0.03*
UCa/UCr
0.22 ± 0.05
0.02 ± 0.01*
Blood
Sodium (mmol/L)
Hormones
Urine
Calculated index
FE(Na, K, Mg, Ca) : fractional excretion of sodium, potassium, magnesium and calcium respectively.
UCa/UCr : radio of urinary calcium and creatinine (mmol/mmol).
Data are expressed in mean ± standard deviation. *p<0.05 compared with the HS group.
25
Table 2. Blood and urine biochemistries before and after 4-week chronic magnesium
supplement
Baseline
(n=12)
4-week After
(n=12)
139.1 ± 2.0
139.6 ± 2.8
Potasium (mmol/L)
2.9 ± 0.3
3.0 ± 0.2
Chloride (mmol/L)
98.2 ± 4.1
99.4 ± 3.9
Magnesium (mmol/L)
0.53 ± 0.06
0.67 ± 0.06*
Calcium, total (mmol/L)
2.4 ± 0.1
2.4 ± 0.1
Calcium, ionized (mmol/L)
1.2 ± 0.1
1.2 ± 0.1
Creatinine (mmol/L)
0.08 ± 0.01
0.08 ± 0.01
Albumin (g/L)
47.7 ± 1.8
48.0 ± 2.0
166.6 ± 13.5
166.7 ± 14.2
5.1 ± 2.4
5.5 ± 3.5
0.25 ± 0.13
0.32 ± 0.15
5.9 ± 0.9
9.1 ± 2.8*
Sodium (mmol/L)
144.0 ± 25
151.0 ± 32
Potassium (mmol/L)
59.0 ± 10
48.0 ± 26
Magnesium (mmol/L)
1.7 ± 0.8
3.6 ± 0.9*
Calcium (mmol/L)
0.25 ± 0.14
0.28 ± 0.11
Creatinine (mmol/L)
13.1 ± 2.3
12.5 ± 4.2
FENa (%)
0.65 ± 0.22
0.69 ± 0.21
FEK (%)
12.4 ± 3.3
10.4 ± 2.2
FEMg (%)
2.10 ± 0.42
3.44 ± 1.21*
FECa (%)
0.13 ± 0.03
0.15 ± 0.05
UCa/UCr
0.019 ± 0.008
0.022 ± 0.011
Blood
Sodium (mmol/L)
Hemoglobin (g/L)
Plasma renin activity (ng/L-s)
Aldosterone (nmol/L)
Intact parathyroid hormone (ng/L)
Urine
FE(Na, K, Mg, Ca) : fractional excretion of sodium, potassium, magnesium and calcium respectively;
UCa/UCr : radio of urinary calcium and creatinine (mmol/mmol).
Data are expressed in mean ± standard deviation. *p<0.05 compared with baseline data.
26
Figure legends
Figure 1. The 24-hour time course of urinary calcium and magnesium excretion after 1-hour
magnesium sulfate (MgSO4) infusion.
27
Figure 1.
28