Contribution of thick ascending limb and distal convoluted tubule to glucose-induced hypercalciuria in healthy controls.

Carbohydrates increase kidney stone risk and increase urine calcium and magnesium. We hypothesize that the effects of glucose as an allosteric modulator of calcium-sensing receptors may mediate this effect. Six healthy subjects were on a low-sodium diet before consuming 100 g of glucose beverage. Timed fasting (3) and postglucose (6) urine and blood samples were collected every 30 min. Urine composition and serum markers were measured and microvesicular abundance of tubular transport proteins (NHE3, NKCC2, NCC, and TRPV5) were quantified. Postglucose, serum glucose, and insulin rose rapidly with a parallel increase in calcium and magnesium excretion and no change in fractional excretion of sodium. Both serum parathyroid hormone (PTH) and urine TRPV5 fell in the postglucose periods. The rise in the calcium and magnesium excretion likely occurred primarily in the thick ascending limb where they are both under control of the calcium-sensing receptor. The fall in PTH and TRPV5 support the role of glucose as an allosteric modulator of calcium-sensing receptor.NEW & NOTEWORTHY Sugar increases urine calcium and magnesium as well as kidney stone and bone disease risk. Our study provided new insights into the underlying mechanism as we gave healthy subjects an oral glucose load and used newer tools such as fractional excretion of lithium, serum parathyroid hormone, and microvesicular abundance of tubular transport proteins to characterize the mechanism and identify the thick ascending limb with possible calcium-sensing receptor mediation as a likely contributor to this mechanism.

A survey of hypercalciuria during chemotherapy in acute lymphoblastic leukemia.

BACKGROUND: Urolithiasis is an extremely rare complication in childhood acute lymphoblastic leukemia (ALL), and some reports have implicated corticosteroids during chemotherapy as a risk factor for it. However, only a few reports have analyzed urinary electrolytes in this context. METHODS: We retrospectively analyzed 55 patients with ALL who underwent chemotherapy between October 2007 and January 2019. Their median age was 9.3 years (range, 0.3-24.0 years) with 30 males and 25 females. Lineages were B-cell precursor ALL (BCP-ALL) in 42 patients, T-cell in nine and others in four patients. All patients received chemotherapy based on the Berlin-Frankfurt-Münster regimen. RESULTS: Forty-nine out of the 55 ALL patients exhibited hypercalciuria at least once during chemotherapy. Moreover, 36 patients with BCP-ALL, who were receiving identical Berlin-Frankfurt-Münster-based regimens, exhibited significantly high urinary calcium excretion immediately following high-dose glucocorticoid administration. Among the 55 ALL patients, urolithiasis was observed in one patient, a 6-year-old boy with BCP-ALL who developed urolithiasis at reinduction chemotherapy just after cessation of high-dose dexamethasone administration. CONCLUSIONS: Nearly 90% of the ALL patients studied developed hypercalciuria during chemotherapy in strong association with corticosteroid administration.

Predictive and prognostic value of magnesium serum level in FOLFIRI plus cetuximab or bevacizumab treated patients with stage IV colorectal cancer: results from the FIRE-3 (AIO KRK-0306) study.

Magnesium wasting is a frequent side effect of epidermal growth factor receptor (EGFR)-antibody treatment as magnesium-absorption mechanisms are dependent on EGFR signaling. EGFR-inhibition results in decreased renal reabsorption. There is evidence that hypomagnesemia during cetuximab treatment correlates with response. The prognostic role of hypomagnesemia during bevacizumab treatment has not been studied yet. Here, we evaluate the prognostic value of hypomagnesemia in patients with metastatic colorectal cancer treated with FOLFIRI plus cetuximab or bevacizumab as first-line therapy. A total of 391 of 752 patients of the firstline irinotecan study population had magnesium levels measured at baseline and for the first three cycles (6 weeks) of treatment. Of those, 240 had Rat Sarkoma wildtype tumors. Overall hypomagnesemia was more common in the cetuximab compared to the bevacizumab arm (80 vs. 43%, P < 0.005). During therapy, magnesium showed a time-dependent decrease to 80% of baseline in the cetuximab and to 89% in the bevacizumab arm. Whereas magnesium continued to decrease over time in the cetuximab-treated patients, it remained stable in the bevacizumab-treated. Overall response rate (ORR) was associated with higher magnesium at week 6 (20.9 vs. 79.1%, P = 0.041). Bevacizumab-treated patients with magnesium levels below the median value at week 6 had a significantly longer progression-free survival (PFS; 11.7 vs. 9.9 months, P = 0.034; hazard ratio 0.73) and a trend towards longer overall survival (OS) (29.6 vs. 23.2 months, P = 0.089; hazard ratio 0.77). Hypomagnesemia at predefined time points and magnesium nadir had no significant effect on ORR, OS and PFS in the cetuximab arm. Our data show different magnesium kinetics in patients with metastatic colorectal cancer treated with cetuximab or bevacizumab. For patients treated with cetuximab, hypomagnesemia did not have an impact on response and survival. Hypomagnesemia might have a prognostic value in bevacizumab treatment.

Growth suppression of human oral cancer cells by candidate agents for cetuximab-side effects.

Cetuximab, an inhibitor of the epidermal growth factor receptor that is used widely to treat human cancers including oral squamous cell carcinoma (OSCC), has characteristic side effects of skin rash and hypomagnesemia. However, the mechanisms of and therapeutic agents for skin rashes and hypomagnesemia are still poorly understood. Our gene expression profiling analyses showed that cetuximab activates the p38 MAPK pathways in human skin cells (human keratinocyte cell line [HaCaT]) and inhibits c-Fos-related signals in human embryonic kidney cells (HEK293). We found that while the p38 inhibitor SB203580 inhibited the expression of p38 MAPK targets in HaCaT cells, flavagline reactivated c-Fos-related factors in HEK293 cells. It is noteworthy that, in addition to not interfering with the effect of cetuximab by both compounds, flavagline has additive effect for OSCC growth inhibition in vivo. Collectively, our results indicate that combination of cetuximab and these potential therapeutic agents for cetuximab-related toxicities could be a promising therapeutic strategy for patients with OSCC.

Hypomagnesemia and Survival in Patients with Ovarian Cancer Who Received Chemotherapy with Carboplatin.

BACKGROUND: Hypomagnesemia is a known side effect of several antineoplastic agents, but its impact on outcomes of patients with cancer is not well understood. We examined whether magnesium abnormalities affect survival in patients with ovarian cancer who receive chemotherapy containing carboplatin. MATERIALS AND METHODS: We included patients with advanced ovarian cancer who had undergone surgery and chemotherapy between January 1, 2004, and December 31, 2014, at our institution. Inclusion criteria were age 18 years or older, pathology of high-grade serous carcinoma, first treatment (surgery or chemotherapy) within 60 days of diagnosis, and chemotherapy containing carboplatin. The final cohort consisted of 229 patients. Vital signs and laboratory tests were recorded at baseline and during the treatment course. The associations between magnesium abnormalities (and other clinical characteristics) and survival were analyzed. RESULTS: The median patient age was 64 years. Higher baseline heart rate (beats per minute; hazard ratio [HR] = 1.02, p = .002) and greater frequency of hypomagnesemia during the treatment course (HR = 1.05, p = .002) were significantly associated with shorter survival independent of completeness of tumor reduction (HR = 1.60, p = .02), and International Federation of Gynecology and Obstetrics stage (HR = 1.63, p = .01). CONCLUSION: Baseline heart rate and the frequency of hypomagnesemia episodes during treatment are prognostic of survival for patients with advanced ovarian cancer receiving carboplatin-containing chemotherapy and tumor reductive surgery. Future research is needed for strategies to detect and prevent hypomagnesemia in this patient population. IMPLICATIONS FOR PRACTICE: Despite standard laboratory tests and intravenous magnesium replacement prior to each cycle of chemotherapy, hypomagnesemia remains a common side effect of platinum-based chemotherapy. This study revealed that frequent occurrence of hypomagnesemia during the course of treatment including carboplatin-containing chemotherapy and tumor reductive surgery was strongly predictive of shorter survival in patients with advanced ovarian cancer. Strategies to effectively mitigate hypomagnesemia, such as more frequent detection, dietary recommendations, and timely replacement, should be considered in the overall cancer treatment plan for these patients.

Effects of Tributyltin (TBT) on Rat Bone and Mineral Metabolism.

BACKGROUND/AIMS: Tributyltin (TBT) is an organotin (OTs) and biohazard organometallic pollutant. Recently our group has shown that TBT, even in very low doses, has deleterious effects on several tissues most likely due to its role as an endocrine-disrupting molecule. Other studies have confirmed that OT exposure could be responsible for neural, endocrine, and reproductive dysfunctions via in vitro and in vivo models. However, TBT effects on bone lack concise data despite the fact that bone turnover is regulated by endocrine molecules, such as parathormone (PTH), estrogen (E2), etc. Our group has already shown that TBT disrupts adrenal and female gonadal functions. METHODS: We studied the effects of TBT on bone metabolism and structure using DXA, microCT scan, and SEM. We also determined the calcium (Ca²âº) and phosphate (Pi) metabolism in TBT-treated rats as well as some biomarkers for bone formation and resorption. RESULTS: Surprisingly, we found that TBT leads to higher bone mineral density (BMD) although lesions in spinal bone were observed by either microCT scan or SEM. Biomarkers for bone resorption, such as the urinary deoxipyridinolines (DPD) excretion ratio was increased in TBT-treated animals versus mock-treated controls. Osteocalcin (OC) and alkaline phosphatase (AP) are markers of bone formation and are also elevated suggesting that the bone matrix suffers from a higher turnover. Serum Ca²âº (total and ionized) do not changed by TBT treatment although hypercalciuria is observed. CONCLUSION: It is known that Sn atoms have three valence states (Sn²âº, Sn³âº, and Sn4⁺); hence, we hypothesized that Sn (more likely Sn²âº) could be competing with Ca²âº and/or Mg²âº in hydroxyapatite mineral matrix to disturb bone turnover. Further work is needed to confirm this hypothesis.

Uromodulin is expressed in the distal convoluted tubule, where it is critical for regulation of the sodium chloride cotransporter NCC.

Uromodulin, the most abundant protein in normal urine, is essentially produced by the cells lining the thick ascending limb. There it regulates the activity of the cotransporter NKCC2 and is involved in sodium chloride handling and blood pressure regulation. Conflicting reports suggested that uromodulin may also be expressed in the distal convoluted tubule (DCT) where its role remains unknown. Using microdissection studies combined with fluorescent in situ hybridization and co-immunostaining analyses, we found a significant expression of uromodulin in mouse and human DCT at approximately 10% of thick ascending limb expression levels, but restricted to the early part of the DCT (DCT1). Genetic deletion of Umod in mouse was reflected by a major shift in NCC activity from the DCT1 to the downstream DCT2 segment, paralleled by a compensatory expansion of DCT2. By increasing the distal sodium chloride and calcium ion load with chronic furosemide administration, an intrinsic compensatory defect in the DCT from Umod-/- compared to wild type mice was found manifested as sodium wasting and hypercalciuria. In line, co-expression studies in HEK cells suggested a facilitating role for uromodulin in NCC phosphorylation, possibly via SPAK-OSR1 modulation. These experiments demonstrate a significant expression of uromodulin in the early part of mouse and human DCT. Thus, biosynthesis of uromodulin in the DCT1 is critical for its function, structure and plasticity, suggesting novel links between uromodulin, blood pressure control and risk of kidney stones.

Proton pump inhibitors not associated with hypomagnesemia, regardless of dose or concomitant diuretic use.

BACKGROUND AND AIM: Proton pump inhibitors (PPIs) are among the most commonly prescribed medications worldwide, with dramatic efficacy for upper gastrointestinal acid-related disorders. In recent years, however, the safety of long-term PPI use has been questioned. One issue based on scant and conflicting literature is the possibility of PPI-related hypomagnesemia. Our purpose was to assess for any clinically significant alteration in serum magnesium levels in large groups of patients taking different PPIs in varying doses, with or without diuretics. METHODS: This was a retrospective review of patient records at time of hospitalization, from February 2012 to December 2014. Two thousand four hundred patients were randomly selected from a pool of 12 058 magnesium levels performed at or within 24 h of hospital admission. Patients were categorized in six groups based on outpatient PPI and/or diuretic use. The main outcome studied was hypomagnesemia, defined as serum magnesium level < 1.6 mg/dL. RESULTS: Mean magnesium levels were normal in PPI users (1.84 ± 0.29 mg/dL [normal 1.6 to 2.5 mg/dL]) and PPI nonusers (1.85 ± 0.30 mg/dL), P = 0.40, and there was no statistical difference in the prevalence of hypomagnesemia (14.7% vs 15.1%, P = 0.77). In separate groups, there were also no significant differences in serum magnesium levels between those taking PPIs of varying doses, with or without concomitant diuretics, and those not taking PPIs or diuretics. CONCLUSION: Regardless of PPI dosage or concomitant diuretics prescribed, magnesium levels were unaffected. Routine screening of serum magnesium in PPI patients appears unnecessary.

Hypercalcemia and hypercalciuria during denosumab treatment in children with osteogenesis imperfecta type VI.

Children with osteogenesis imperfecta (OI) type VI often have high fracture rates despite the current standard treatment with bisphosphonates. Subcutaneous injections of denosumab have been proposed as an alternative treatment approach, but safety data on denosumab in children are limited. Here we describe fluctuations in bone and mineral metabolism during denosumab treatment in four children with OI type VI who started denosumab (basic protocol: 1 mg per kg body mass every 3 months) between 1.9 and 9.0 years of age, after having received intravenous bisphosphonates previously. All four children developed hypercalciuria during active denosumab therapy. In two children aged 3.9 and 4.6 years, episodes of hypercalcemia were observed between 7 and 12 weeks after the preceding denosumab injection. During times when the interval between denosumab injections was increased to 6 months for clinical reasons, lumbar spine bone mineral density z-scores decreased rapidly. It appears that the duration of action of denosumab is short and variable in children with OI type VI. These observations call into question the concept that denosumab can be used as a stand-alone alternative to bisphosphonates to treat children with OI.

Calcifediol (25-hydroxyvitamin D) improvement and calcium-phosphate metabolism of alendronate sodium/vitamin D3 combination in Chinese women with postmenopausal osteoporosis: a post hoc efficacy analysis and safety reappraisal.

BACKGROUND: Vitamin D (VD) insufficiency or deficiency is a frequent comorbidity in Chinese women with postmenopausal osteoporosis (PMO). The present study aimed to investigate 25-hydroxyvitamin D [25(OH) D] improvement and calcium-phosphate metabolism in Chinese PMO patients treated with 70 mg of alendronate sodium and 5600 IU of vitamin D3 (ALN/D5600). METHODS: Chinese PMO women (n = 219) were treated with 12-month ALN/D5600 (n = 111) or calcitriol (n = 108). Changes in 25(OH) D at month 12 were post hoc analyzed by the baseline 25 (OH) D status using the longitudinal analysis. The main safety outcome measures included serum calcium and phosphate and 24-h urine calcium, and the repeated measures mixed model was used to assess the frequencies of the calcium-phosphate metabolic disorders. RESULTS: Absolute change in mean serum 25(OH) D level was the greatest in VD-deficient patients and least in VD-sufficient patients at months six and 12 (both, P < 0.01). Serum calcium level remained significantly lower in the ALN/D5600 treatment group than in the calcitriol treatment group throughout the 12 months. Mean 24-h urine calcium slightly increased in the ALN/D5600 treatment group and significantly increased in the calcitriol treatment group (+ 1.1 and + 0.9 mmol/L at months six and 12; both, P < 0.05). Calcitriol treatment was associated with more frequent hypercalciuria at month six (9.4% vs. 18.5%, P = 0.05), but not at month 12 (12.3% vs. 13.0%). CONCLUSION: Baseline VD status predicted 25(OH) D improvement in PMO patients on 12-month ALN/D5600 treatment. The daily use of 0.25 µg of calcitriol was associated with more frequent hypercalciuria at month six, compared to ALN/5600 treatment, necessitating the safety re-evaluation of calcitriol at a higher dosage.

[A genomic study of adult-onset idiopathic hypoparathyroidism in Chinese by targeted next-generation sequencing].

OBJECTIVE: Several genes have been recognized to be associated with non-surgical hypoparathyroidism. Data about gene mutations in adult-onset hypoparathyroidism patients is lacking. This study was designed to screen gene mutation in adult-onset hypoparathyroidism in Chinese through the targeted next-generation sequencing (NGS). METHODS: We recruited 17 patients with adult-onset hypoparathyroidism who were regularly followed or newly diagnosed at our centre during the past one year. Nine of them developed hypercalciuria during the treatment with calcium and vitamin D. Eight of them were newly diagnosed with no treatment. Targeted NGS was performed to screen 11 related genes, including AIRE, AP2S1, CASR, CLDN16, FAM111A, GATA3, GCM2, PTH, TBCE, TBX1 and TRPM6. RESULTS: A novel homozygosis mutation of GCMB gene[c.130G>A (p.G44S)]was identified which was predicted to be deleterious by PolyPhen2. The patient was a 36-year-old woman who suffered from paroxysmal carpopedal spasms for ten years. Before treatment, the serum calcium and phosphorus was 1.48 mmol/L and 2.29 mmol/L, respectively.Parathyroid hormonel (PTH) concentration was lower than 3.0 ng/L. Intracranial calcification and cataract were also identified. She developed hypercalciuria during treatment with calcium and vitamin D. She had no physical deformity or family history of hypoparathyroidism. CONCLUSIONS: In this study, the genetic defect was only identified in 1 patient (5.9%). In adult-onset hypoparathyroidism without other diagnostic clues, the gene mutation screening as the first choice to clarify the etiology was not recommended.

A phase I study to determine the maximum tolerated dose and safety of oral LR-103 (1α,24(S)Dihydroxyvitamin D2) in patients with advanced cancer.

BACKGROUND: The objective of this study was to determine the maximum tolerated dose and safety of LR-103, a Vitamin D analogue, in patients with advanced cancer. METHODS: In Step A, patients received oral LR-103 once daily in 14-day cycles with intra-patient dose escalation per accelerated dose escalation design. Dose limiting toxicity for Step A was defined as ≥grade 2 hypercalcemia and/or >grade 2 other toxicities. Starting dose was 5 µg/day. Step B used a 3+3 design starting at Step A maximum tolerated dose with 28-day cycles. Dose limiting toxicity was defined as ≥grade 3 hypercalcemia or any grade 3 or 4 non-hematologic toxicity, except hypercalciuria. RESULTS: Twenty-one patients were enrolled; eight were treated in Step A. At dose level 3 (15 µg/day), two patients had dose limiting toxicity. One had grade 4 hyperuricemia. The other had grade 4 GGT plus grade 3 alkaline phosphatase, fatigue and urinary tract infection (UTI). Dose level 2 (10 µg/day) was the maximum tolerated dose for Step A and was starting dose for Step B. The dose was escalated to dose level 5 (30 µg/day) with a patient experiencing grade 3 dose limiting toxicity of hypercalcemia. The study was discontinued before reaching the maximum tolerated dose due to sponsor decision. Modest increases in serum osteocalcin and calcium and decrease in parathyroid hormone were noted. Best response was stable disease; four patients were on therapy for six months or longer. CONCLUSION: Step A dose limiting toxicities limited accelerated dose escalation. The maximum tolerated dose of LR-103 was not reached prior to study termination and this agent is no longer being developed.

Persistence of 1,25D-induced hypercalciuria in alendronate-treated genetic hypercalciuric stone-forming rats fed a low-calcium diet.

Genetic hypercalciuric stone-forming (GHS) rats demonstrate increased intestinal Ca absorption, increased bone resorption, and reduced renal tubular Ca reabsorption leading to hypercalciuria and all form kidney stones. GHS have increased vitamin D receptors (VDR) at these sites of Ca transport. Injection of 1,25(OH)2D3 (1,25D) leads to a greater increase in urine (u)Ca in GHS than in control Sprague-Dawley (SD), possibly due to the additional VDR. In GHS the increased uCa persists on a low-Ca diet (LCD) suggesting enhanced bone resorption. We tested the hypothesis that LCD, coupled to inhibition of bone resorption by alendronate (alen), would eliminate the enhanced 1,25D-induced hypercalciuria in GHS. SD and GHS were fed LCD and half were injected daily with 1,25D. After 8 days all were also given alen until euthanasia at day 16. At 8 days, 1,25D increased uCa in SD and to a greater extent in GHS. At 16 days, alen eliminated the 1,25D-induced increase in uCa in SD. However, in GHS alen decreased, but did not eliminate, the 1,25D-induced hypercalciuria, suggesting maximal alen cannot completely prevent the 1,25D-induced bone resorption in GHS, perhaps due to increased VDR. There was no consistent effect on mRNA expression of renal transcellular or paracellular Ca transporters. Urine CaP and CaOx supersaturation (SS) increased with 1,25D alone in both SD and GHS. Alen eliminated the increase in CaP SS in SD but not in GHS. If these results are confirmed in humans with IH, the use of bisphosphonates, such as alen, may not prevent the decreased bone density observed in these patients.

Proton pump inhibitors and hospitalization with hypomagnesemia: a population-based case-control study.

BACKGROUND: Some evidence suggests that proton pump inhibitors (PPIs) are an under-appreciated risk factor for hypomagnesemia. Whether hospitalization with hypomagnesemia is associated with use of PPIs is unknown. METHODS AND FINDINGS: We conducted a population-based case-control study of multiple health care databases in Ontario, Canada, from April 2002 to March 2012. Patients who were enrolled as cases were Ontarians aged 66 years or older hospitalized with hypomagnesemia. For each individual enrolled as a case, we identified up to four individuals as controls matched on age, sex, kidney disease, and use of various diuretic classes. Exposure to PPIs was categorized according to the most proximate prescription prior to the index date as current (within 90 days), recent (within 91 to 180 days), or remote (within 181 to 365 days). We used conditional logistic regression to estimate the odds ratio for the association of outpatient PPI use and hospitalization with hypomagnesemia. To test the specificity of our findings we examined use of histamine H2 receptor antagonists, drugs with no causal link to hypomagnesemia. We studied 366 patients hospitalized with hypomagnesemia and 1,464 matched controls. Current PPI use was associated with a 43% increased risk of hypomagnesemia (adjusted odds ratio, 1.43; 95% CI 1.06-1.93). In a stratified analysis, the risk was particularly increased among patients receiving diuretics, (adjusted odds ratio, 1.73; 95% CI 1.11-2.70) and not significant among patients not receiving diuretics (adjusted odds ratio, 1.25; 95% CI 0.81-1.91). We estimate that one excess hospitalization with hypomagnesemia will occur among 76,591 outpatients treated with a PPI for 90 days. Hospitalization with hypomagnesemia was not associated with the use of histamine H2 receptor antagonists (adjusted odds ratio 1.06; 95% CI 0.54-2.06). Limitations of this study include a lack of access to serum magnesium levels, uncertainty regarding diagnostic coding of hypomagnesemia, and generalizability of our findings to younger patients. CONCLUSIONS: PPIs are associated with a small increased risk of hospitalization with hypomagnesemia among patients also receiving diuretics. Physicians should be aware of this association, particularly for patients with hypomagnesemia. Please see later in the article for the Editors' Summary.

Vitamin D and fetal-neonatal calcium homeostasis: findings from a randomized controlled trial of high-dose antenatal vitamin D supplementation.

BACKGROUND: There is current interest in the maternal-fetal effects of antenatal vitamin D supplementation, yet little data regarding vitamin D's role in neonatal calcium homeostasis. We determined to assess the effect of high-dose antenatal vitamin D supplementation on fetal and neonatal calcium concentrations. METHODS: In a double-blinded, placebo-controlled trial in Bangladesh, 160 pregnant women were randomized to oral vitamin D3 (35,000 IU/wk) or placebo from 26 to 29 wk of gestation. RESULTS: Total serum calcium (Ca) was higher in cord blood of those supplemented vs. placebo (2.66 ± 0.1 vs. 2.61 ± 0.2 mmol/l; P = 0.04), but the difference in albumin-adjusted calcium was not statistically significant. Change in Ca concentration from birth to day 3 of life was attenuated by vitamin D (-0.10 ± 0.17) compared with placebo (-0.22 ± 0.18 mmol/l; P = 0.02). Maternal 25-hydroxyvitamin D (25(OH)D) (P = 0.04) and cord 25(OH)D (P < 0.01) were associated with day 3 infant Ca, suggesting that the effect of supplementation was mediated by change in maternal-infant vitamin D status. Six infants in each of the supplemented and placebo groups had transient hypercalcemia/hypercalcuria; in all the hypercalcemia/hypercalcuria was asymptomatic, spontaneously resolved, and unassociated with nephrocalcinosis at 1 mo of life. CONCLUSION: High-dose antenatal third-trimester vitamin D supplementation attenuated the early postnatal calcium nadir, without increasing the risk of postnatal hypercalcemia.

"Ghosts in my body": Seizure-like presentation of hypocalcemic tetany secondary to hypomagnesemia in a patient receiving cetuximab therapy for metastatic medulloblastoma.

Cetuximab, a monoclonal antibody specific for epidermal growth factor receptor, is increasingly used off-label and in early-phase trials for pediatric malignancies. Here, we report a patient with metastatic medulloblastoma receiving therapy with cyclophosphamide, vinblastine, and cetuximab. During evaluation for possible seizures, he was noted to be severely hypocalcemic, hypokalemic, and hypomagnesemic, a consequence of the blockade of renal epidermal growth factor receptor expression. His symptoms rapidly abated with intravenous electrolyte repletion. This case highlights the clinical heterogeneity of tetany and the importance of careful laboratory screening for known adverse effects of chemotherapy, particularly when newer biological agents are used off-study in combination chemotherapeutic regimens.

Calcium nephrolithiasis induced by topiramate.

Topiramate is an approved drug to treat seizures, but its indications have been extended to other diseases of the nervous system and as an adjuvant to chronic pain. We present four cases of topiramate-induced nephrolithiasis from 2006-2012 in women whose treatment was prescribed for pain control and as a mood stabilizer at doses of 250-300 mg/day. In two cases, the lithiasis was caused by calcium phosphate (patite) and in the other two cases by oxalate and calcium phosphate. The most common metabolic alteration was an alkaline pH, followed by hypocitraturia. The drug was discontinued in two patient; it was reduced in one and was maintained in the fourth. An increase in fluid and potassium citrate intake was prescribed. In patients starting treatment with topiramate, an adequate control and prevention of nephrolithiasis should be performed due to the risk of mixed tubular acidosis and hypocitraturia. to the risk of mixed tubular acidosis and hypocitraturia.

[A 78-year-old female patient with dizziness, apraxia and seizure under proton pump inhibitor therapy]. / 78-jährige Patientin mit Unwohlsein, Schwindel, Apraxie und Krampfanfall unter Protonenpumpeninhibitortherapie.

We report about a female patient with severe hypomagnesemia under therapy with proton pump inhibitors (PPI) who presented with a cerebral seizure. Chronic use of PPIs can cause hypomagnesemia. Because of mostly unspecific symptoms which become symptomatic only with severe deficiency, the disease pattern is underdiagnosed. Hypomagnesemia is currently coming increasingly more to the forefront of medical literature.

1,25(OH)2D3-enhanced hypercalciuria in genetic hypercalciuric stone-forming rats fed a low-calcium diet.

The inbred genetic hypercalciuric stone-forming (GHS) rats exhibit many features of human idiopathic hypercalciuria and have elevated levels of vitamin D receptors (VDR) in calcium (Ca)-transporting organs. On a normal-Ca diet, 1,25(OH)2D3 (1,25D) increases urine (U) Ca to a greater extent in GHS than in controls [Sprague-Dawley (SD)]. The additional UCa may result from an increase in intestinal Ca absorption and/or bone resorption. To determine the source, we asked whether 1,25D would increase UCa in GHS fed a low-Ca (0.02%) diet (LCD). With 1,25D, UCa in SD increased from 1.2 ± 0.1 to 9.3 ± 0.9 mg/day and increased more in GHS from 4.7 ± 0.3 to 21.5 ± 0.9 mg/day (P < 0.001). In GHS rats on LCD with or without 1,25D, UCa far exceeded daily Ca intake (2.6 mg/day). While the greater excess in UCa in GHS rats must be derived from bone mineral, there may also be a 1,25D-mediated decrease in renal tubular Ca reabsorption. RNA expression of the components of renal Ca transport indicated that 1,25D administration results in a suppression of klotho, an activator of the renal Ca reabsorption channel TRPV5, in both SD and GHS rats. This fall in klotho would decrease tubular reabsorption of the 1,25D-induced bone Ca release. Thus, the greater increase in UCa with 1,25D in GHS fed LCD strongly suggests that the additional UCa results from an increase in bone resorption, likely due to the increased number of VDR in the GHS rat bone cells, with a possible component of decreased renal tubular calcium reabsorption.

Association of hypomagnesemia with inferior survival in a phase III, randomized study of cetuximab plus best supportive care versus best supportive care alone: NCIC CTG/AGITG CO.17.

BACKGROUND: Cetuximab-induced hypomagnesemia has been associated with improved clinical outcomes in advanced colorectal cancer (CRC). We explored this relationship from a randomized clinical trial of cetuximab plus best supportive care (BSC) versus BSC alone in patients with pretreated advanced CRC. PATIENTS AND METHODS: Day 28 hypomagnesemia grade (0 versus ≥1) and percent reduction (<20% versus ≥20%) of Mg from baseline was correlated with outcome. RESULTS: The median percentage Mg reduction at day 28 was 10% (-42.4% to 63.0%) for cetuximab (N = 260) versus 0% (-21.1% to 25%) for BSC (N = 251) [P < 0.0001]. Grade ≥1 hypomagnesemia and ≥20% reduction from baseline at day 28 were associated with worse overall survival (OS) [hazard ratio, HR 1.61 (95% CI 1.12-2.33), P = 0.01 and 2.08 (95% CI 1.32-3.29), P = 0.002, respectively] in multivariate analysis including grade of rash (0-1 versus 2+). Dyspnea (grade ≥3) was more common in patients with ≥20% versus < 20% Mg reduction (68% versus 45%; P = 0.02) and grade 3/4 anorexia were higher in patients with grade ≥1 hypomagnesemia (81% versus 63%; P = 0.02). CONCLUSIONS: In contrast to prior reports, cetuximab-induced hypomagnesemia was associated with poor OS, even after adjustment for grade of rash.