Functional hypoparathyroidism and parathyroid hormone end-organ resistance in human magnesium deficiency

Gitelman syndrome with primary hyperparathyroidism: A case report

BACKGROUND

Gitelman syndrome (GS) is a rare autosomal recessive inherited salt-losing tubulopathy, typically devoid of hypercalcemia. Herein, we described one patient of GS presenting with hypercalcemia concomitant with primary hyperparathyroidism (PHPT).

METHODS

On September 28, 2020, a middle-aged female patient was admitted to our hospital with a 12-year history of hypokalemia and hypomagnesemia. Laboratory examinations unveiled hypokalemia with renal potassium wasting, hypomagnesemia, metabolic alkalosis, hypocalciuria, and gene sequencing revealed a homozygous mutation in SLC12A3 (c.179C > T [p.T60M]). Subsequently, the diagnosis of GS was confirmed. In addition, the patient exhibited hypercalcemia and elevated levels of parathyroid hormone. Parathyroid ultrasound revealed left parathyroid hyperplasia, consistent with PHPT. Following aggressive treatment with potassium chloride and magnesium oxide, her serum potassium rose to 3.23 mmol/L, serum magnesium was 0.29 mmol/L, and her joint pain was relieved.

RESULTS

Based on the patient's medical history, laboratory findings, and gene sequencing results, the definitive diagnosis was GS concomitant with PHPT.

CONCLUSION

PHPT should be taken into consideration when patients diagnosed with GS exhibit hypercalcemia. While the serum potassium level readily exceeded the target threshold, correcting hypomagnesemia proved challenging, primarily because PHPT augments urinary magnesium excretion.

Diuretic Use and Serum Phosphate: Rotterdam Study and UK Biobank

Purpose

Hypophosphatemia (serum phosphate < 0.80 mmol/L) leads to musculoskeletal complaints. The most common drugs linked to hypophosphatemia are thiazide and loop diuretics, but studies in the general population are lacking. Our aim was to study associations between diuretic use and serum phosphate in the Rotterdam Study (RS), a population-based cohort study, with replication in UK Biobank (UKBB).

Methods

Associations between thiazide and loop diuretic use and serum phosphate and odds of hypophosphatemia were analyzed with cross-sectional multivariate linear and logistic regression in participants without chronic kidney disease in the RS and UKBB. Analyses were adjusted for age, sex, and body mass index (BMI) and pooled in 3 RS cohorts with further adjustment for cohort and serum potassium, which was not available in UKBB.

Results

Thiazide diuretics were associated with lower serum phosphate in both sexes. This association lost significance in RS females after adjustment for BMI and in males after adjustment for serum potassium. Thiazide diuretics increased odds of hypophosphatemia in females in both cohorts and in males in UKBB only. Loop diuretics were associated with lower serum phosphate in females but not males. Adjustment for BMI attenuated these associations. Associations between loop diuretics and increased odds of hypophosphatemia in females lost significance after BMI adjustment.

Conclusion

Thiazides, but not loop diuretics, and increased BMI and decreased serum potassium should be considered as contributing factors in subjects with hypophosphatemia. Further studies are needed to replicate the findings and elucidate the potential role of hypokalemia as a mediator of this effect.

Proton pump inhibitors, bone and phosphocalcic metabolism

Proton pump inhibitors (PPIs) are widely used for acid-related gastrointestinal disorders; however, concerns have arisen about their prolonged and inappropriate use. Although generally considered safe, recent evidence has linked PPI use with an increased risk of kidney disease, stomach cancer, pneumonia, dementia, cardiovascular events and potential bone health problems. This systematic review examines the effects of PPIs on bone health, including osteoporosis and changes in phosphocalcic and magnesium metabolism, through a comprehensive analysis of the recent literature. The relationship between PPIs, bone mineral density and fracture risk, especially in populations with comorbidities, is complex and we propose a focus based on recent data. Studies of the effect of PPI use on bone mineral density have shown mixed results and require further investigation. Observational studies have indicated an increased risk of fractures, particularly vertebral fractures, associated with PPI use. Recent meta-analyses have confirmed an association between PPI use and hip fractures with a dose-dependent effect. More recently, PPIs have been associated with serious disturbances in phosphocalcic and magnesium metabolism that require careful management and discontinuation. Proton pump inhibitor-induced hypomagnesemia (PPIH) is a well-established phenomenon. In addition, hypocalcemia secondary to severe hypomagnesemia has been described. Despite growing evidence of PPI-related risks, further research is essential to better understand the complex mechanisms, as most data are from observational studies and do not establish a causal relationship. This review emphasizes the need for judicious prescription practices, particularly in long-term use scenarios and rheumatological contexts.

Rare cause of recurrent hypocalcaemia and functional hypoparathyroidism due to hypomagnesaemia caused by TRPM6 gene mutation

Magnesium is essential for the functioning and release of parathyroid hormone. Therefore, its deficiency can present as functional hypoparathyroidism. This case report describes a rare inherited disorder called congenital hypomagnesaemia with secondary hypocalcaemia due to TRPM6 gene mutation. This disease clinically and biochemically mimics hypoparathyroidism. However, unlike hypoparathyroidism, it can be treated only by long-term oral magnesium supplements. The patient presented to us with recurrent hypocalcaemic convulsions. The laboratory picture in each admission was similar to that of hypoparathyroidism. However, the hypocalcaemia persisted, and it was noticed to be associated with persistent hypomagnesaemia. A defect in the tubular magnesium reabsorption was postulated and a genetic analysis of the patient was done, which revealed a TRPM6 mutation causing hypomagnesaemia by excessive renal excretion of magnesium. The child responded well to oral magnesium supplements and is currently developmentally appropriate for her age and thriving well.

An assessment of serum magnesium levels in critically ill patients: A prospective observational study

Background

A specific magnesium level is essential to be maintained to ensure appropriate neuromuscular excitability and cardiac function; an increase or decrease in its levels usually leads to critical abnormality. Hypomagnesemia in critically ill patients has many potential ramifications and is found to be an important factor in hindering their recovery. Thus, the study aimed to assess the serum magnesium levels in critically ill participants and explore its effect on their condition.

Methods

A prospective observational study was conducted for 21 months, from February 2019 to October 2020, among all critically ill participants admitted to the medical intensive care unit (ICU) of a tertiary care hospital. The Acute Physiology and Chronic Health Evaluation II score questionnaire was used to determine the severity of their condition and blood samples were collected within 24 h of their ICU admission for analysis.

Results

One hundred participants were enrolled, of which 40% were between the age group of 46 and 65 years and 71% were males. Among all participants with hypomagnesemia, 52% were diabetic, 19% had a history of alcohol use disorder, and 27% had normal calcium and potassium levels. Hypomagnesemia significantly correlated with a longer duration of ICU stay among participants.

Conclusion

A significant correlation was observed between hypomagnesemia and increased ICU length of stay and mortality but not the duration of mechanical ventilation. Monitoring and appropriate supplementation of serum magnesium is recommended to limit further comorbidity and mortality in the critical care setting.

Cisplatin Nephrotoxicity: Novel Insights Into Mechanisms and Preventative Strategies

Cisplatin is a highly effective chemotherapeutic agent that has been used for more than 50 years for a variety of cancers; however, its use is limited by toxicity, including nephrotoxicity. In this in-depth review, we discuss the incidence of cisplatin-associated acute kidney injury, as well as common risk factors for its development. Cisplatin accumulates in the kidney tubules and causes AKI through various mechanisms, including DNA damage, oxidative stress, and apoptosis. We also discuss the spectrum of nephrotoxicity, including acute and chronic impairment of kidney function, electrolyte disturbances, and thrombotic microangiopathy. We discuss the limited options for the diagnosis, prevention, and management of these complications, along with factors that may impact future therapy with or without cisplatin. We conclude with directions for future research in this expanding and important area.

Association between Serum Magnesium and Fractures: A Systematic Review and Meta-Analysis of Observational Studies

Magnesium, an essential cation for numerous cellular processes, is a major component of bone. However, its relationship with the risk of fractures is still uncertain. The present systematic review and meta-analysis aim to investigate the impact of serum Mg on the risk of incident fractures. A systematic search was conducted using several databases including PubMed/Medline and Scopus from inception to 24 May 2022, including observational studies investigating serum Mg and the incidence of fractures considered as outcomes. Abstract and full-text screenings, data extractions, and risk of bias assessments were conducted by two investigators independently. Any inconsistencies were resolved by consensus with a third author. The Newcastle–Ottawa Scale was used to assess the study quality/risk of bias. Among 1332 records initially screened, 16 were retrieved as full-texts; of them, four papers were included in the systematic review with a total of 119,755 participants. We found that lower serum Mg concentrations were associated with a significantly higher risk of incident fractures (RR = 1.579; 95%CI: 1.216–2.051; p = 0.001; I2 = 46.9%). Our systematic review with meta-analysis suggests a strong association of serum Mg concentrations with incident fractures. Further research is needed to confirm our results among other populations and to assess whether serum Mg is potentially relevant in the prevention of fractures, which continue to increase and represent a significant health burden due to the associated disability.

Endocrine sequelae of hematopoietic stem cell transplantation: Effects on mineral homeostasis and bone metabolism

Hematopoietic stem cell transplantation (HSCT) is an established therapeutic strategy for the treatment of malignant (leukemia and lymphoma) and non-malignant (thalassemia, anemia, and immunodeficiency) hematopoietic diseases. Thanks to the improvement in patient care and the development of more tolerable conditioning treatments, which has extended the applicability of therapy to the elderly, a growing number of patients have successfully benefited from HSCT therapy and, more importantly, HSCT transplant-related mortality has consistently reduced in recent years. However, concomitantly to long term patient survival, a growing incidence of late HSCT-related sequelae has been reported, being variably associated with negative effects on quality of life of patients and having a non-negligible impact on healthcare systems. The most predominantly observed HSCT-caused complications are chronic alterations of the endocrine system and metabolism, which endanger post-operative quality of life and increase morbidity and mortality of transplanted patients. Here, we specifically review the current knowledge on HSCT-derived side-effects on the perturbation of mineral metabolism; in particular, the homeostasis of calcium, focusing on current reports regarding osteoporosis and recurrent renal dysfunctions that have been observed in a percentage of HSC-transplanted patients. Possible secondary implications of conditioning treatments for HSCT on the physiology of the parathyroid glands and calcium homeostasis, alone or in association with HSCT-caused renal and bone defects, are critically discussed as well.

Clinical Factors Associated with Serum Magnesium Concentration in Patients Undergoing Peritoneal Dialysis: A Single-Center Observational Study

Purpose

Magnesium (Mg) is an essential element that is associated with various physiological functions, such as maintenance of blood pressure, muscle contraction, and nerve function. In patients undergoing hemodialysis, hypomagnesemia is associated with cardiovascular and all-cause mortality. However, in patients undergoing peritoneal dialysis (PD), clinical factors associated with Mg have not been fully investigated.

Patients and Methods

Clinical factors including anthropometric data, comorbidities, laboratory data, medications, and dialysis methods were collected from the medical records of patients undergoing PD. The associations of these factors with the serum Mg concentration were investigated by univariate and multivariate analyses.

Results

Sixty patients undergoing PD were investigated. The univariate analysis showed that the serum Mg concentration was significantly associated with treatment by hybrid PD (daily PD + once-weekly hemodialysis) (β = 0.264, P = 0.04), administration of phosphate binders (β = 0.294, P = 0.02), the serum C-reactive protein concentration (β = -0.318, P = 0.01), the serum potassium (K) concentration (β = 0.451, P < 0.01), and the serum intact parathormone concentration (β = -0.333, P = 0.01). The multivariate analysis using these factors showed an independent association between the serum Mg and K concentrations (β = 0.333, P = 0.01).

Conclusion

The serum Mg concentration was independently associated with the serum K concentration in patients undergoing PD.

Influencing factors of serum magnesium in CKD5 patients: A multicenter study in southern China

INTRODUCTION

Magnesium (Mg) disturbances are related to cardiac, bone, and renal patient mortality. In this study, we compared biochemical markers in hemodialysis (HD) and peritoneal dialysis (PD) patients and explored the influencing factors of serum Mg in stage 5 chronic kidney disease (CKD5) patients.

MATERIAL AND METHODS

All 598 patients with CKD5 from three medical centers in South China were recruited into this prospective cohort study from March 1, 2018, to January 31, 2021. Our study recorded the clinical characteristics and laboratory data of the patients.

RESULTS

Hemodialysis patients (0.99 ± 0.19 mmol/L) had a higher mean serum Mg level than PD patients (0.86 ± 0.20 mmol/L; p < 0.01). Regression analysis showed that only corrected calcium (Ca), phosphate (P), Ca/Mg, Ca × P, albumin (Alb), total protein and creatine (Cr) predicted Mg levels in CKD5 patients (p < 0.01). Ca/Mg predicts hypomagnesemia with 78% sensitivity and 85% specificity in CKD5 patients. The AUC value corresponding to Ca/Mg was 0.88.

CONCLUSIONS

This multicenter study in southern China showed that for all CKD5 patients, corrected Ca and Alb had a significant positive effect on serum Mg, while Ca/Mg had a significant negative effect on serum Mg. In 123 HD patients, Ca × P was positively associated with Mg while Ca/Mg and P were negatively associated with Mg. In 398 PD patients, Ca × P, Alb, and total protein were positively associated with Mg while Ca/Mg and P were negatively associated with Mg. In 77 non-dialysis patients, corrected Ca, Cr, and total protein were positively associated with Mg while Ca/Mg was negatively associated with Mg. Furthermore, Ca/Mg might be another useful technique to monitor blood Mg levels in CKD5 patients.

CLINICAL TRIAL REGISTRATION

ChiCTR1800014557.

Hypomagnesaemia causing functional hypoparathyroidism in rheumatic mitral stenosis leading to sudden cardiac arrest in a young woman

A 23-year-old young woman with a known history of valvular heart disease of rheumatic origin, post balloon mitral valvotomy 5 years ago, presented with fever, palpitations and breathlessness. ECG showed atrial fibrillation with fast ventricular rate. A 2D transthoracic echocardiography showed severe restenosis of mitral valve and moderate left ventricular dysfunction. She was admitted for evaluation of fever and control of the ventricular rate. She sustained cardiac arrest due to unknown cause and was resuscitated. When the patient sustained another cardiac arrest, torsades de pointes was detected on the monitor. Blood parameters showed hypomagnesaemia, hypocalcaemia and hypokalaemia, causing functional hypoparathyroidism which was treated with intravenous magnesium, oral calcium and vitamin D supplements. Timely detection of a tachyarrhythmia due to a ventricular origin was life saving, which is rarely seen in patients with rheumatic heart disease and mitral stenosis.

Identification of p.Arg205Cys in CASR in an autosomal dominant hypocalcaemia type 1 pedigree: A case report

RATIONALE

Autosomal dominant hypocalcaemia type 1 (ADH1) is a genetic disease characterized by benign hypocalcemia, inappropriately low parathyroid hormone levels and mostly hypercalciuria. It is caused by the activating mutations of the calcium-sensing receptor gene (CASR), which produces a left-shift in the set point for extracellular calcium.

PATIENT CONCERNS

A 50-year-old man presenting with muscle spasms was admitted into the hospital. He has a positive familial history for hypocalcemia. Auxiliary examinations demonstrated hypocalcemia, hyperphosphatemia, normal parathyroid hormone level and nephrolithiasis. A missense heterozygous variant in CASR, c 613C > T (p. Arg205Cys) which has been reported in a familial hypocalciuric hypercalcemia type 1 patient was found in the patient's genotype. It is the first time that this variant is found associating with ADH1. The variant is predicted vicious by softwares and cosegregates with ADH1 in this pedigree. CASR Arg205Cys was deduced to be the genetic cause of ADH1 in the family.

DIAGNOSIS

The patient was diagnosed with ADH1 clinically and genetically.

INTERVENTIONS

Oral calcitriol, calcium and hydrochlorothiazide were prescribed to the patient.

OUTCOMES

After the treatments for 1 week, the patient's symptom was improved and the re-examination revealed serum calcium in the normal range. A 3-month follow-up showed his symptom was mostly relieved.

LESSONS

The variant of CASR Arg205Cys, responsible for ADH1 in this family, broadened the genetic spectrum of ADH1. Further and more studies are required to evaluate the correlation between genotype and phenotype in ADH1 patients.

Serum Magnesium and Fractional Exhaled Nitric Oxide in Relation to the Severity in Asthma-Chronic Obstructive Pulmonary Disease Overlap

Serum concentrations of magnesium and manganese may be associated with increased chronic obstructive pulmonary disease exacerbation risk. However, associations with other aspects of asthma-chronic obstructive pulmonary disease overlap, pulmonary function test results and health status, have been studied less extensively. The aim of this study was to investigate the associations between serum concentrations of trace elements and T lymphocyte subsets, FeNO, and COPD-related questionnaire scores in individuals with ACO and the potential impact of these parameters on lung function. All the patients met the diagnostic criteria of ACO and were divided into two groups (group A, mild-moderate; group B, severe-very severe) by their specific characteristics. Pulmonary function testing and serum Mg and serum Mn and FeNO were measured. Four hundred sixty-five patients were screened, and 42 were included. Group A had significantly higher Mg and Fe concentrations than group B. No significant differences were seen in the serum concentration of any other trace element between the two groups. Serum Mg and Mn were correlated with FEV1% predicted (p < 0.01). Group A had a significantly higher FeNO concentration than group B (p = 0.005). The scores on CAT (p = 0.011) and mMRC (p = 0.008) in group A were lower than in group B. The low-FeNO group had a significantly lower concentration of serum Mg than the high-FeNO group (p = 0.03). Pulmonary function declined faster (p < 0.05) in the low-FeNO group than the high-FeNO group. Serum Mg concentration may indicate protective effects against lung function loss in ACO. This implies that FeNO might be a biomarker for identifying individuals with ACO who might benefit from inhaled corticosteroid therapy. Serum Mg and FeNO were associated with ACO severity. However, their role in guiding personalised treatment of individuals with ACO needs to be further investigated.

The Perilous PPI: Proton Pump Inhibitor as a Cause of Clinically Significant Hypomagnesaemia

Proton pump inhibitors (PPIs) are the mainstay of therapy for all gastric acid related diseases and are commonly used in current clinical practice. Although widely regarded as safe, PPIs have been associated with a variety of adverse effects, including hypomagnesaemia. The postulated mechanism of PPI-related hypomagnesaemia involves inhibition of intestinal magnesium absorption via transient receptor potential melastin (TRPM) 6 and 7 cation channels. PPIinduced hypomagnesaemia (PPIH) has become a well recognized phenomenon since it was first reported in 2006. Clinical concerns arise from growing number of case reports presenting PPIH as a consequence of long-term PPI use, with more than 30 cases published to date.

In this article, we report 2 cases of PPIH associated with the use of pantoprazole. Both patients presented with severe hypomagnesaemia and hypocalcaemia. One of them had associated hypokalemia and cardiac arrhythmia. A casual relation with PPIs postulated and supported by resolution of electrolyte abnormalities after discontinuation of PPIs.

Magnesium in Infectious Diseases in Older People

Reduced magnesium (Mg) intake is a frequent cause of deficiency with age together with reduced absorption, renal wasting, and polypharmacotherapy. Chronic Mg deficiency may result in increased oxidative stress and low-grade inflammation, which may be linked to several age-related diseases, including higher predisposition to infectious diseases. Mg might play a role in the immune response being a cofactor for immunoglobulin synthesis and other processes strictly associated with the function of T and B cells. Mg is necessary for the biosynthesis, transport, and activation of vitamin D, another key factor in the pathogenesis of infectious diseases. The regulation of cytosolic free Mg in immune cells involves Mg transport systems, such as the melastatin-like transient receptor potential 7 channel, the solute carrier family, and the magnesium transporter 1 (MAGT1). The functional importance of Mg transport in immunity was unknown until the description of the primary immunodeficiency XMEN (X-linked immunodeficiency with Mg defect, Epstein-Barr virus infection, and neoplasia) due to a genetic deficiency of MAGT1 characterized by chronic Epstein-Barr virus infection. This and other research reporting associations of Mg deficit with viral and bacterial infections indicate a possible role of Mg deficit in the recent coronavirus disease 2019 (COVID-19) and its complications. In this review, we will discuss the importance of Mg for the immune system and for infectious diseases, including the recent pandemic of COVID-19.

Prevalence and Determinants of a Blunted Parathyroid Hormone Response in Young Saudi Women with Vitamin D Deficiency: A Cross-Sectional Study

Vitamin D deficiency is highly prevalent among the Saudi population. Increased parathyroid hormone (PTH) secretion is an appropriate homeostatic response to correct the resultant hypocalcemia. However, not all vitamin D deficiency patients have increased PTH levels. This study determined the prevalence of a blunted PTH response to vitamin D deficiency among apparently healthy young Saudi women and assessed anthropometric and biochemical factors associated with this response by performing a secondary analysis of data obtained from a cross-sectional study conducted at the "Center of Excellence for Osteoporosis research." Overall, 315 women (aged 20-45 years) with vitamin D deficiency (serum 25-hydroxyvitamin D (25(OH)D) levels <30 nmol/L) were included. They were divided into two groups according to the laboratory cutoff value of PTH (<7 or ≥7 pmol/L), and anthropometric and biochemical characteristics of both groups were compared. Women with a blunted PTH response (n = 62, 19.7%) had a significantly lower body mass index (BMI) (P < 0.001) and smaller waist circumference (P=0.001). They also had significantly higher serum 25(OH)D (P=0.001), corrected serum calcium (P < 0.001), and phosphate (P=0.003) levels than those with an elevated PTH response (n = 253, 80.3%). Multiple logistic regression analysis showed that lower BMI (OR = 0.925; 95% CI: 0.949-0.987) and higher 25(OH)D (OR = 1.068; 95% CI: 1.014-1.124) and serum calcium (OR = 8.600; 95% CI: 1.614-45.809) levels were significantly associated with a blunted PTH response (R ² = 0.178). A blunted PTH response to vitamin D deficiency is mainly observed among women with lower BMI. Higher serum calcium and 25(OH)D levels and lower BMI were significant predictors of a blunted PTH response, which may indicate that these subjects are adapting to lower 25(OH)D levels and maintaining normal calcium levels without the need to increase PTH secretion. The mechanisms underlying this adaptation are unclear, and future studies to explore these mechanisms are warranted.

Hypomagnesemia and incidence of osteoradionecrosis in patients with head and neck cancers

BACKGROUND

We aimed to determine whether hypomagnesemia predicts osteoradionecrosis development in patients with squamous cell carcinoma of the oropharynx and oral cavity who received platinum-based concurrent chemoradiation with or without induction therapy.

METHODS

We reviewed data from patients with head and neck cancers who had undergone chemoradiation with weekly cisplatin/carboplatin between January 1, 2010 and December 31, 2014 at our institution. Pathologic features, laboratory test results, disease stage, and social histories were recorded. The association between hypomagnesemia and osteoradionecrosis was analyzed controlling for known confounding factors.

RESULTS

Hypomagnesemia during cancer treatment was associated with osteoradionecrosis development (HR = 2.72, P = .037) independent of total radiation dose (HR = 1.07, P = .260) and smoking history (HR = 2.05, P = .056) among the patients who received platinum-based induction chemotherapy followed by concurrent chemoradiation.

CONCLUSIONS

Hypomagnesemia was predictive of the development of osteoradionecrosis in patients with cancers of the oropharynx and oral cavity receiving platinum-based induction followed by concurrent chemoradiation.

Hypocalcaemia following denosumab in prostate cancer: A clinical review

OBJECTIVES

Denosumab is often used in men with advanced prostate cancer to prevent skeletal-related events, but can be associated with severe hypocalcaemia. Our objective was to review the pathophysiology, identify risk factors and provide recommendations for prevention and management of denosumab-associated hypocalcaemia.

DESIGN

We reviewed the literature regarding denosumab-associated severe hypocalcaemia, defined as necessitating hospitalization for intravenous calcium treatment, in the context of prostate cancer.

PATIENTS

Men with prostate cancer with severe denosumab-associated hypocalcemia.

RESULTS

We identified 20 men with prostate cancer with severe denosumab-associated hypocalcemia, including the present case. Median age (range) was 70 years (45-86). All had skeletal metastases and presented with symptomatic hypocalcemia 16 days (4-35) after the initial (n = 18) or second (n = 2) denosumab treatment, with a serum total calcium of 1.36 mmol/L (1.13-1.91). The key risk factor was presence of active osteoblastic metastases, evidenced by elevated serum alkaline phosphatase, 838 U/L (58-2620) and supportive imaging. Other risk factors reported in some men included vitamin D deficiency (<50 nmol/L), 25-OH vitamin D 44 nmol/L (22-81), renal impairment, serum creatinine 103 μmol/L (62-1131) and hypomagnesaemia, 0.82 mmol/L (0.29-1.20). Men received intravenous calcium infusions for 16 days (1-90), and median total intravenous elemental calcium requirements were 3.17 g (0.47-26.65).

CONCLUSIONS

Denosumab treatment in men with metastatic prostate cancer can be associated with life-threatening hypocalcaemia requiring prolonged hospitalization for intravenous calcium treatment. Modifiable risk factors should be corrected before denosumab administration. In men with active osteoblastic metastases, consideration should be given to delay denosumab treatment until underlying disease activity is controlled, and/or be administered with close monitoring and proactive treatment with calcium and calcitriol.

A patient with extensive cerebral calcification due to pseudohypoparathyroidism: a case report

BACKGROUND

Pseudohypoparathyroidism(PHP) is a heterogeneous group of disorders due to impaired activation of c AMP dependant pathways following binding of parathyroid hormone (PTH) to its receptor. In PHP end organ resistance to PTH results in hypocalcaemia, hyperphosphataemia and high PTH levels.

CASE PRESENTATION

A 59 year old male presented with a history of progressive impairment of speech and unsteadiness of gait for 1 week and acute onset altered behavior for 1 day and one episode of generalized seizure. His muscle power was grade four according to MRC (medical research council) scale in all limbs and Chovstek's and Trousseau's signs were positive. Urgent non contrast computed tomography scan of the brain revealed extensive bilateral cerebral and cerebellar calcifications. A markedly low ionized calcium level of 0.5 mmol/l, an elevated phosphate level of 9.5 mg/dl (reference range: 2.7-4.5 mg/dl) and an elevated intact PTH of 76.3 pg/l were noted. His renal functions were normal. His hypocalcemia was accentuated by the presence of hypomagnesaemia. His 25 hydroxy vitamin D level was only marginally low which could not account for severe hypocalcaemia. A diagnosis of pseudohypoparathyroidism without phenotypic defects, was made due to hypocalcaemia and increased parathyroid hormone levels with cerebral calcifications. The patient was treated initially with parenteral calcium which was later converted to oral calcium supplements. His coexisting Vitamin D deficiency was corrected with 1αcholecalciferol escalating doses. His hypomagnesaemia was corrected with magnesium sulphate parenteral infusions initially and later with oral preparations. With treatment there was a significant clinical and biochemical response.

CONCLUSION

Pseudohypoparathyroidism can present for the first time in elderly resulting in extensive cerebral calcifications. Identification and early correction of the deficit will result in both symptomatic and biochemical response.

Learning Physiology From Inherited Kidney Disorders

The identification of genes causing inherited kidney diseases yielded crucial insights in the molecular basis of disease and improved our understanding of physiological processes that operate in the kidney. Monogenic kidney disorders are caused by mutations in genes coding for a large variety of proteins including receptors, channels and transporters, enzymes, transcription factors, and structural components, operating in specialized cell types that perform highly regulated homeostatic functions. Common variants in some of these genes are also associated with complex traits, as evidenced by genome-wide association studies in the general population. In this review, we discuss how the molecular genetics of inherited disorders affecting different tubular segments of the nephron improved our understanding of various transport processes and of their involvement in homeostasis, while providing novel therapeutic targets. These include inherited disorders causing a dysfunction of the proximal tubule (renal Fanconi syndrome), with emphasis on epithelial differentiation and receptor-mediated endocytosis, or affecting the reabsorption of glucose, the handling of uric acid, and the reabsorption of sodium, calcium, and magnesium along the kidney tubule.

A novel SLC12A3 homozygous c2039delG mutation in Gitelman syndrome with hypocalcemia

Background

Gitelman syndrome (GS) is a rare autosomal recessive renal tubular disease, caused by mutations in the SLC12A3 gene, which encodes the renal thiazide-sensitive Na/Cl cotransporter (NCCT) in the distal renal tubule.

Case presentation

A 23-year-old woman was admitted with limb numbness, recurrent tetany and palpitation. Laboratory tests showed hypokalemic alkalosis, hypomagnesemia, hypocalcemia and secondary hyperaldosteronism, as well as hypocalciuria and transient decreased PTH. Next-generation sequencing detected a novel homozygous mutations c.2039delG in the SLC12A3 gene, and her father and children were all heterozygous carriers.

Conclusion

We reported a case of GS with a novel homozygous frame-shift mutation of SLC12A3, and reviewed recent literatures about diagnosis, differential diagnosis and treatments. Hypocalcemia in Gitelman syndrome is rare, and may be related to inhibited PTH secretion induced by hypomagnesemia.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1163-3) contains supplementary material, which is available to authorized users.

Conventional Treatment of Hypoparathyroidism

Conventional therapy of hypoparathyroidism consists of oral calcium and either activated vitamin D or vitamin D supplements at varying doses. Although adjusting dosing of calcium and/or activated vitamin D or vitamin D itself, the serum calcium should be obtained weekly or monthly depending on the clinical situation. Calcium supplementation in hypoparathyroidism usually consists of calcium carbonate because it is 40% elemental calcium by weight. However, calcium citrate (21% elemental calcium) is indicated for patients with achlorhydria and proton pump inhibitor therapy. Many clinicians prefer to uptitrate the activated form of vitamin D to reduce the amount of calcium supplementation.

Hypocalcemic disorders

Calcium is vital for life, and extracellular calcium concentrations must constantly be maintained within a precise concentration range. Low serum calcium (hypocalcemia) occurs in conjunction with multiple disorders and can be life-threatening if severe. Symptoms of acute hypocalcemia include neuromuscular irritability, tetany, and seizures, which are rapidly resolved with intravenous administration of calcium gluconate. However, disorders that lead to chronic hypocalcemia often have more subtle manifestations. Hypoparathyroidism, characterized by impaired secretion of parathyroid hormone (PTH), a key regulatory hormone for maintaining calcium homeostasis, is a classic cause of chronic hypocalcemia. Disorders that disrupt the metabolism of vitamin D can also lead to chronic hypocalcemia, as vitamin D is responsible for increasing the gut absorption of dietary calcium. Treatment and management options for chronic hypocalcemia vary depending on the underlying disorder. For example, in patients with hypoparathyroidism, calcium and vitamin D supplementation must be carefully titrated to avoid symptoms of hypocalcemia while keeping serum calcium in the low-normal range to minimize hypercalciuria, which can lead to renal dysfunction. Management of chronic hypocalcemia requires knowledge of the factors that influence the complex regulatory axes of calcium homeostasis in a given disorder. This chapter discusses common and rare disorders of hypocalcemia, symptoms and workup, and management options including replacement of PTH in hypoparathyroidism.

Association of Hypomagnesemia with Hypocalcemia after Thyroidectomy

BACKGROUND

Hypocalcemia is one of the most common acceptable complications in postoperative period after thyroidectomy. Hypomagnesemia has been recognized after parathyroid surgery, and it has not been studied extensively after thyroidectomy. The aim of this study was to estimate magnesium and calcium ion levels in patients undergoing thyroidectomy and to evaluate the association of hypomagnesemia with hypocalcemia after thyroidectomy. A prospective study was conducted in Government Medical College, Calicut, from December 2012 to November 2013.

MATERIALS AND METHODS

all patients had undergone total/near-total/subtotal thyroidectomy. Pre- and postoperative at 24 h and serum calcium and magnesium were measured by automate electrolyte analyzer. Clinical findings of hypocalcemia were recorded. Statistical analysis was done using SPSS software, version 17.0. Unpaired student t-test was used. Pearson Chi-square test or Fisher's exact test was used to compare the percentage for categorical variables.

RESULTS

In our study, 58% of the patients developed hypocalcemia, biochemical and/or symptomatic (S. Ca <8.5). About 34% of patients developed hypomagnesemia, biochemical and/or symptomatic (S. Mg <1.7). About 30% of patients developed both hypocalcemia and hypomagnesemia. About 24% of patients developed symptoms of both hypocalcemia and hypomagnesemia.

DISCUSSION

Thyroidectomy patients were at a risk of transient and permanent hypoparathyroidism because of chances of parathyroid resection during operation. Transient hypocalcemia and hypomagnesemia occur frequently after total thyroidectomy. It is important to monitor both calcium and magnesium levels after total thyroidectomy and to correct deficiencies to facilitate prompt resolution of symptoms.

CONCLUSION

There is an association of hypomagnesemia with hypocalcemia after thyroidectomy.

De novo a novel variant of CaSR gene in a neonate with congenital hypoparathyroidism

Autosomal-dominant hypocalcemia with hypercalciuria (ADHH) is a genetic disease characterized by hypoparathyroidism with hypercalciuria. Most patients with ADHH have calcium-sensing receptor (CaSR) gene mutations. The CaSR gene controls parathyroid secretions, and mutations in this gene can be detected via changes in serum calcium level. The activating mutation of the CaSR gene results in familial or sporadic ADHH. Most activating mutations of the CaSR gene are reportedly de novo missense mutations. This is the first case report of a novel activating variant of the CaSR gene in a neonate with congenital hypoparathyroidism with hypomagnesemia and hypercalciuria. We also report the 3-month follow-up management of the patient.

The effect of dietary magnesium and caseinphosphopeptides on bone metabolism in rats

The effect of dietary magnesium (Mg) or caseinphosphopeptides (CPPs) on bone metabolism has been reported. However, few studies have investigated the effects of simultaneous supplementation of Mg and CPPs. Sixty-three 3-week-old Sprague-Dawley male rats were divided into seven groups and fed a specified diet for 45 days. Body characteristics, bone physicochemical indicators, and bone metabolism indicators relative to bone metabolism were analyzed. We found that, first, a dietary Mg deficiency resulted in increased bone formation and decreased bone resorption. Second, dietary Mg or CPP supplementation promoted bone formation and prevented bone resorption. Third, dietary Mg supplementation with CPPs also functioned to enhance bone formation and prevent bone resorption. There were synergistic effects on femur length, serum parathyroid hormone level and urinary deoxypyridinoline of the HS-Mg-CPP group (0.2% Mg, 0.1% CPPs). The increase in the femur length of the HS-Mg-CPP group compared with the control group was 6% which was much higher than that of HS-Mg (1%) or CPPs (5%). The induction in serum parathyroid hormone content in the HS-Mg-CPP group was 33% compared with the control group which was higher than that of the induction of the HS-Mg (19%) or CPP (23%) group. The induction in the deoxypyridinoline content of the HS-Mg-CPP (43%) group compared with the control group was remarkably higher than that of HS-Mg (8%) or CPPs (16%). Overall our results demonstrated that high doses of Mg (0.2%) and CPPs (0.1%) in combination produced synergistic effects on femur length, serum parathyroid hormone level and urinary deoxypyridinoline in rats, which is important for a better understanding of the effect of Mg and CPPs on bone metabolism.

Hypomagnesemia in critically ill patients

BACKGROUND

Magnesium (Mg) is essential for life and plays a crucial role in several biochemical and physiological processes in the human body. Hypomagnesemia is common in all hospitalized patients, especially in critically ill patients with coexisting electrolyte abnormalities. Hypomagnesemia may cause severe and potential fatal complications if not timely diagnosed and properly treated, and associate with increased mortality.

MAIN BODY

Mg deficiency in critically ill patients is mainly caused by gastrointestinal and/or renal disorders and may lead to secondary hypokalemia and hypocalcemia, and severe neuromuscular and cardiovascular clinical manifestations. Because of the physical distribution of Mg, there are no readily or easy methods to assess Mg status. However, serum Mg and the Mg tolerance test are most widely used. There are limited studies to guide intermittent therapy of Mg deficiency in critically ill patients, but some empirical guidelines exist. Further clinical trials and critical evaluation of empiric Mg replacement strategies is needed.

CONCLUSION

Patients at risk of Mg deficiency, with typical biochemical findings or clinical symptoms of hypomagnesemia, should be considered for treatment even with serum Mg within the normal range.

Subclinical magnesium deficiency: a principal driver of cardiovascular disease and a public health crisis

Because serum magnesium does not reflect intracellular magnesium, the latter making up more than 99% of total body magnesium, most cases of magnesium deficiency are undiagnosed. Furthermore, because of chronic diseases, medications, decreases in food crop magnesium contents, and the availability of refined and processed foods, the vast majority of people in modern societies are at risk for magnesium deficiency. Certain individuals will need to supplement with magnesium in order to prevent suboptimal magnesium deficiency, especially if trying to obtain an optimal magnesium status to prevent chronic disease. Subclinical magnesium deficiency increases the risk of numerous types of cardiovascular disease, costs nations around the world an incalculable amount of healthcare costs and suffering, and should be considered a public health crisis. That an easy, cost-effective strategy exists to prevent and treat subclinical magnesium deficiency should provide an urgent call to action.

Development of a Multivariate Predictive Model to Estimate Ionized Calcium Concentration from Serum Biochemical Profile Results in Dogs

BACKGROUND

Ionized calcium concentration is the gold standard to assess calcium status in dogs, but measurement is not always available.

OBJECTIVES

(1) To predict ionized calcium concentration from biochemical results and compare the diagnostic performance of predicted ionized calcium concentration (piCa) to those of total calcium concentration (tCa) and 2 corrected tCa formulas; and (2) to study the relationship between biochemical results and variation of measured ionized calcium concentration (miCa).

ANIMALS

A total of 1,719 dogs with both miCa and biochemical profile results available.

METHODS

Cross-sectional study. Using 1,200 dogs, piCa was determined using a multivariate adaptive regression splines model. Its accuracy and performance were tested on the remaining 519 dogs.

RESULTS

The final model included creatinine, albumin, tCa, phosphorus, sodium, potassium, chloride, alkaline phosphatase, triglycerides, and age, with tCa, albumin, and chloride having the highest impact on miCa variation. Measured ionized calcium concentration was better correlated with piCa than with tCa and corrected tCa and had higher overall diagnostic accuracy to diagnose hypocalcemia and hypercalcemia, but not significantly for hypercalcemia. For hypercalcemia, piCa was as sensitive (64%) but more specific (99.6%) than tCa and corrected tCa. For hypocalcemia, piCa was more sensitive (21.8%) and as specific (98.4%) as tCa. Positive and negative predictive values of piCa were high for both hypercalcemia (90% and 98%, respectively) and hypocalcemia (70.8% and 87.7%, respectively).

CONCLUSIONS AND CLINICAL IMPORTANCE

Predicted ionized calcium concentration can be obtained from readily available biochemical and patient results and seems more useful than tCa and corrected tCa to assess calcium disorders in dogs when miCa is unavailable. Validation on external data, however, is warranted.

Multiple Electrolyte and Metabolic Emergencies in a Single Patient

While some electrolyte disturbances are immediately life-threatening and must be emergently treated, others may be delayed without immediate adverse consequences. We discuss a patient with alcoholism and diabetes mellitus type 2 who presented with volume depletion and multiple life-threatening electrolyte and metabolic derangements including severe hyponatremia (serum sodium concentration [S_Na] 107 mEq/L), hypophosphatemia ("undetectable," <1.0 mg/dL), and hypokalemia (2.2 mEq/L), moderate diabetic ketoacidosis ([DKA], pH 7.21, serum anion gap [S_AG] 37) and hypocalcemia (ionized calcium 4.0 mg/dL), mild hypomagnesemia (1.6 mg/dL), and electrocardiogram with prolonged QTc. Following two liters of normal saline and associated increase in S_Na by 4 mEq/L and serum osmolality by 2.4 mosm/Kg, renal service was consulted. We were challenged with minimizing the correction of S_Na (or effective serum osmolality) to avoid the osmotic demyelinating syndrome while replacing volume, potassium, phosphorus, calcium, and magnesium and concurrently treating DKA. Our management plan was further complicated by an episode of significant aquaresis. A stepwise approach was strategized to prioritize and correct all disturbances with considerations that the treatment of one condition could affect or directly worsen another. The current case demonstrates that a thorough understanding of electrolyte physiology is required in managing complex electrolyte disturbances to avoid disastrous outcomes.

Hypomagnesemia and Chemotherapy, Diagnostic Dilemma, and Treatment Challenge: Case Report and Literature Review

Magnesium is the second most common intracellular cation after potassium and plays pivotal role in the majority of metabolic process. Several studies have shown the prevalence of hypomagnesemia ranging from 2.5% to 12% in general population and even up to 60% in intensive care unit patients. Hypomagnesemia might be more prevalent in patients with cancer owing to a combination of several factors such as gastrointestinal loss, renal loss, poor intake, and use of certain chemotherapeutic drugs. It is imperative that we identify the exact cause of hypomagnesemia to aid and guide treatment. We report a case of a 63-year-old white woman with hypomagnesemia who was undergoing treatment for metastatic colon cancer. The chemotherapy regimen was with FOLFIRI (folinic acid, 5-fluorouracil, and irinotecan) and bevacizumab. This was followed by maintenance therapy with Xeloda (capecitabine). Her hypomagnesium was attributed to her chemotherapy. During our workup, the renal fractional excretion of magnesium was found to be low excluding the cause as renal wasting. This patient's hypomagnesemia could very well be explained by gastrointestinal losses (diarrhea) from short bowel after colectomy, her chemotherapeutic agents and metformin, as well as poor oral intake from medications, or malignancy itself.

Postoperative hypomagnesaemia is not associated with hypocalcemia in thyroid cancer patients undergoing total thyroidectomy plus central compartment neck dissection

BACKGROUND

The literature remains scarce and controversial regarding the association of hypomagnesaemia and hypocalcemia after total thyroidectomy. This study aims to assess this association in thyroid cancer patients underwent total thyroidectomy (TT) plus central compartment neck dissection (CCND).

METHOD

All consecutive thyroid cancer patients who underwent TT plus CCND were retrospectively reviewed through a prospectively collected database between October 2015 and June 2016 in a tertiary referral hospital. The univariate and multivariate analysis were performed to identify the significant predictors for hypocalcemia.

RESULTS

A total of 237 patients were included. The incidence of postoperative biochemical and symptomatic hypocalcemia was 52.3% (124 patients) and 33.8% (80 patients), respectively. Multivariate analysis showed that only postoperative hypoparathyroidism was an independent predictor for biochemical hypocalcemia (HR = 14.37, 95%CI = 6.07-34.0; P < 0.000), while parathyroid gland autotansplantation (HR = 2.02, 95%CI = 1.04-3.91; P = 0.038) and hypoparathyroidism (HR = 7.47, 95%CI = 3.84-14.5; P < 0.000) were independent risk factor for symptomatic hypocalcemia. Postoperative hypomagnesaemia was not significantly associated with the development of hypocalcemia (P > 0.05).

CONCLUSION

Postoperative hypomagnesaemia was not an independent predictor of hypocalcemia after total thyroidectomy. It seems to be unnecessary to routinely monitor the magnesium levels before and after thyroid surgery.

Suppression of Parathyroid Hormone in a Patient with Severe Magnesium Depletion

Hypomagnesemia is often associated with coexisting electrolyte abnormalities like hypokalemia and hypocalcemia. Hypocalcemia has been shown to be secondary to hypoparathyroidism induced by hypomagnesemia. Here, we discuss a case of a patient with severe hypomagnesemia and associated hypocalcemia. A 38-year-old lady was admitted to the hospital for weakness of lower extremities and an eventual fall. The exam was significant for decreased motor strength and some paresthesias. The laboratory data was significant for hypomagnesemia, hypokalemia, and low parathyroid level in the face of hypocalcemia. After replacing magnesium, the parathyroid hormone levels normalized and led to eventual correction of calcium levels without any additional calcium replacement therapy. There was complete symptom resolution with correction of electrolyte abnormalities. This case highlights the importance of looking for all associated abnormalities in a patient with hypomagnesemia and starting the replacement therapy by first replacing the magnesium and then the others as needed. Replacing the magnesium alone may correct the hypoparathyroidism and eliminate the need for calcium replacement.

Review of Hypoparathyroidism

Hypoparathyroidism is a rare endocrine disorder in which parathyroid hormone (PTH) production is abnormally low or absent, resulting in low serum calcium and increased serum phosphorus. The most common cause of hypoparathyroidism is parathyroid gland injury or inadvertent removal during thyroid surgery. Current treatments include supplementation with calcium and active vitamin D, with goal albumin-corrected serum calcium level in the low-normal range of 8-9 mg/dl. Complications of the disease include renal dysfunction, nephrocalcinosis, kidney stones, extracellular calcifications of the basal ganglia, and posterior subcapsular cataracts, as well as low bone turnover and increased bone density. Until January 2015, hypoparathyroidism was the only classic endocrine disease without an available hormone replacement. Recombinant human PTH 1-84, full-length PTH, is now available for a selected group of patients with the disease who are not well controlled on the current standard therapy of calcium and active vitamin D. In addition, the role of PTH replacement on quality of life, intracerebral calcifications, cataracts, improving bone turnover, and reduction of renal complications of the disease remains to be further investigated.

Hypomagnesemia due to two novel TRPM6 mutations

BACKGROUND

Although most hypocalcemia with hypomagenesemia in the neonatal period is due to transient neonatal hypoparathyroidism, magnesium channel defects should also be considered.

CASE

We report a case of persistent hypomagnesemia in an 8-day-old Hispanic male who presented with generalized seizures. He was initially found to have hypomagnesemia, hypocalcemia, hyperphosphatemia and normal parathyroid hormone. Serum calcium normalized with administration of calcitriol and calcium carbonate. Serum magnesium improved with oral magnesium sulfate. However, 1 week after magnesium was discontinued, serum magnesium declined to 0.5 mg/dL. Magnesium supplementation was immediately restarted, and periodic seizure activity resolved after serum magnesium concentration was maintained above 0.9 mg/dL. The child was eventually weaned off oral calcium and calcitriol with persistent normocalemia. However, supraphysiologic oral magnesium doses were necessary to prevent seizures and maintain serum magnesium at the low limit of normal.

METHODS AND RESULTS

As his clinical presentation suggested primary renal magnesium wastage, TRPM6 gene mutations were suspected; subsequent genetic testing revealed the child to be compound heterozygous for TRPM6 mutations.

CONCLUSION

Two novel TRPM6 mutations are described with a new geographic and ethnic origin. This case highlights the importance of recognizing disorders of magnesium imbalance and describing new genetic mutations.

Refractory hypocalcaemia complicating metastatic prostatic carcinoma

A 72-year-old man with a background of ischaemic heart disease was referred to the accident and emergency department with a 1-week history of worsening dyspnoea and lethargy. A chest X-ray revealed a right-sided lobar pneumonia and a prolonged corrected QT interval was noted on his ECG at presentation. Laboratory investigations confirmed severe hypocalcaemia, significant vitamin D deficiency and relative hypoparathyroidism. A markedly elevated prostate-specific antigen was also identified. Bone scintigraphy demonstrated widespread osteoblastic bone metastases. Severe hypocalcaemia persisted despite treatment and he succumbed after 60 days of hospitalisation.

Vitamin D Metabolites and Their Association with Calcium, Phosphorus, and PTH Concentrations, Severity of Illness, and Mortality in Hospitalized Equine Neonates

Background

Hypocalcemia is a frequent abnormality that has been associated with disease severity and outcome in hospitalized foals. However, the pathogenesis of equine neonatal hypocalcemia is poorly understood. Hypovitaminosis D in critically ill people has been linked to hypocalcemia and mortality; however, information on vitamin D metabolites and their association with clinical findings and outcome in critically ill foals is lacking. The goal of this study was to determine the prevalence of vitamin D deficiency (hypovitaminosis D) and its association with serum calcium, phosphorus, and parathyroid hormone (PTH) concentrations, disease severity, and mortality in hospitalized newborn foals.

Methods and Results

One hundred newborn foals ≤72 hours old divided into hospitalized (n = 83; 59 septic, 24 sick non-septic [SNS]) and healthy (n = 17) groups were included. Blood samples were collected on admission to measure serum 25-hydroxyvitamin D₃ [25(OH)D₃], 1,25-dihydroxyvitamin D₃ [1,25(OH) ₂D₃], and PTH concentrations. Data were analyzed by nonparametric methods and univariate logistic regression. The prevalence of hypovitaminosis D [defined as 25(OH)D₃ <9.51 ng/mL] was 63% for hospitalized, 64% for septic, and 63% for SNS foals. Serum 25(OH)D₃ and 1,25(OH) ₂D₃ concentrations were significantly lower in septic and SNS compared to healthy foals (P<0.0001; P = 0.037). Septic foals had significantly lower calcium and higher phosphorus and PTH concentrations than healthy and SNS foals (P<0.05). In hospitalized and septic foals, low 1,25(OH)₂D₃ concentrations were associated with increased PTH but not with calcium or phosphorus concentrations. Septic foals with 25(OH)D₃ <9.51 ng/mL and 1,25(OH) ₂D₃ <7.09 pmol/L were more likely to die (OR=3.62; 95% CI = 1.1-12.40; OR = 5.41; 95% CI = 1.19-24.52, respectively).

Conclusions

Low 25(OH)D₃ and 1,25(OH)₂D₃ concentrations are associated with disease severity and mortality in hospitalized foals. Vitamin D deficiency may contribute to a pro-inflammatory state in equine perinatal diseases. Hypocalcemia and hyperphosphatemia together with decreased 1,25(OH)₂D₃ but increased PTH concentrations in septic foals indicates that PTH resistance may be associated with the development of these abnormalities.

R990G polymorphism of calcium sensing receptor gene is associated with high parathyroid hormone levels in subjects with vitamin D deficiency: a cross-sectional study

Single nucleotide polymorphisms (SNPs), R990G and A986S of the calcium sensing receptor (CaSR) gene, are shown to influence response of parathyroid hormone (PTH) in subjects with optimal vitamin D levels. This cross-sectional study was conducted in subjects with vitamin D deficiency (VDD) to observe associations between CaSR polymorphisms, plasma iPTH, and serum calcium levels. Adult females (n = 140) with known VDD, intact parathyroid hormone (iPTH), and calcium levels were recruited for genotype analysis. The frequencies of the 986 alleles GG, GT, and TT were 68%, 25%, and 7%, respectively, whereas the frequencies of the 990 alleles AA, AG, and GG were 80%, 8.9%, and 11.1%, respectively. The subjects with GG genotype of R990G polymorphism had higher iPTH levels (148.65 versus 91.47 and 86.1 pg/mL for GG versus AA, AG, resp., P = 0.008) and lower calcium levels (8.4 versus 9.04 and 9.07 mg/dL for GG versus AA, AG, resp., P = 0.002). No such association of A986S polymorphism with plasma iPTH or serum calcium levels was observed in the present study. Patients with VDD bearing the GG genotype of R990G SNPs are prone to have higher iPTH levels and lower calcium.

Estimation of magnesium in patients with functional hypoparathyroidism

CONTEXT

It is evident that about 30-50% of patients with Vitamin D deficiency (VDD) do not manifest develop secondary hyperparathyroidism (SHPT). A number of theories have been proposed to explain this lack of SHPT, including hypomagnesemia.

SETTINGS AND DESIGN

Retrospective review of laboratory database.

MATERIALS AND METHODS

We evaluated the differences in serum magnesium (Mg) levels among those with VDD with or without SHPT. A retrospective review of 6255 laboratory data of bone mineral profiles performed in the period of 2007-2013. After excluding patients with hypercalcemia, renal dysfunction/unknown kidney function and primary hypothyroidism, the remaining 1323 patient data were analyzed. SHPT was defined as serum parathyroid hormone >65 in those with VDD.

STATISTICAL ANALYSIS USED

ANOVA and Wilcoxon tests as appropriate to compare means. Multivariate logistic regression to analyze relation between variables and outcome of SHPT.

RESULTS

We noted that 55% patients (n = 727) had VDD, and among those who had VDD, 23% (n = 170) were hypocalcemic (corrected serum calcium <8.5). Patients with VDD who did not exhibit SHPT were 56% (n = 407). The mean (±standard deviation) serum Mg levels in the entire cohort (n = 1323) was 1.94 ± 0.26 mg/dl and 1.95 ± 0.26 mg/dl in VDD cohort and 2 ± 0.31 mg/dl in the VDD-hypocalcemic cohort. There was no statistical difference in the Mg levels among those with SHPT compared to those without SHPT (P = 0.14). Serum calcium and phosphorus were lower in those with SHPT (P = 0.06 and P < 0.001, respectively). In multivariate logistic regression, serum calcium (P = 0.043), phosphorus (P < 0.001) and severe VDD (P < 0.001) independently correlated with occurrence of SHPT in VDD.

CONCLUSIONS

Serum Mg levels did not explain the functional hypoparathyroidism seen in about half of the patients with VDD. A low normal serum calcium and phosphorus levels are more likely to be associated with VDD patients who develop SHPT.

Hypomagnesaemia associated with long-term use of proton pump inhibitors

Hypomagnesaemia and associated hypocalcaemia and hypoparathyroidism have been increasingly recognised as rare long-term side-effects of proton pump inhibitors (PPIs). The PPIs may inhibit active magnesium (Mg) absorption by interfering with transcellular transient receptor potential melastatin-6 and -7 (TRPM 6 and 7) channels. More recent cell culture studies have suggested concomitant inhibition of passive Mg absorption by omeprazole. After being treated with a range of PPIs, the four patients in our case series developed hypomagnesaemia, which responded to withdrawal of therapy and initiation of Mg replacement. Their clinical course and management demonstrate key aspects of hypomagnesaemia associated with long-term use of PPIs.

Prevalence of hypocalcaemia and its associated features in 22q11·2 deletion syndrome

BACKGROUND

22q11.2 deletion syndrome (22q11.2DS) is a relatively common yet under-recognized genetic syndrome that may present with endocrine features. We aimed to address the factors that contribute to the high prevalence of hypocalcaemia.

METHODS

We investigated hypocalcaemia in a well-characterized sample of 138 adults with 22q11.2DS (65 m, 73 F; mean age 34.2, SD 11.8, years) using laboratory studies and lifelong medical records. Logistic regression modelling was used to identify features associated with lifetime prevalence of hypocalcaemia.

RESULTS

Of the total sample, 111 (80.4%) had a lifetime history of hypocalcaemia. Eleven (84.6%) of 13 subjects with neonatal hypocalcaemia had documented recurrence of hypocalcaemia. Lifetime history of hypocalcaemia was associated with lifetime prevalence of hypoparathyroidism (P < 0.0001) and hypothyroidism (P = 0.04), as statistically independent factors. Hypomagnesaemia was associated with concurrent hypocalcaemic measurements, especially in the presence of concurrent hypoparathyroidism (P = 0.02).

CONCLUSIONS

The results suggest that, in addition to the major effect of hypoparathyroidism, hypothyroidism may play a role in hypocalcaemia in 22q11.2DS and that there is a high recurrence rate of neonatal hypocalcaemia. Hypomagnesaemia may contribute to hypocalcaemia by further suppressing parathyroid hormone (PTH). Although further studies are needed, the findings support regular lifelong follow-up of calcium, magnesium, PTH and TSH levels in patients with 22q11.2DS. At any age, hypocalcaemia with hypoparathyroidism and/or hypothyroidism may suggest a diagnosis of 22q11.2DS.