Can one really measure magnesium deficiency using the short-term magnesium loading test?

Acquired Disorders of Hypomagnesemia

Magnesium disorders are common in clinical practice and when present can manifest clinically as cardiovascular, neuromuscular, or other organ dysfunction. Hypomagnesemia is far more common than hypermagnesemia, which is largely seen in patients with reduced glomerular filtration rates receiving magnesium-containing medications. In addition to inherited disorders of magnesium handling, hypomagnesemia is also seen with excessive gastrointestinal or renal losses and due to medications such as amphotericin B, aminoglycosides, and cisplatin. Laboratory assessment of body magnesium stores largely relies on the measurement of serum magnesium levels that are a poor proxy for total body stores but does correlate with the development of symptoms. Replacement of magnesium can be challenging, with oral replacement strategies being generally more effective at slowly replacing body stores but intravenous replacement being more effective at treating the more life-threatening and severe cases of hypomagnesemia. We conducted a thorough review of the literature using PubMed (1970-2022) and the search terms magnesium, hypomagnesemia, drugs, medications, treatment, and therapy. In the absence of clear data on optimal management of hypomagnesemia, we have made recommendations on magnesium replacement based on our clinical experience.

[Magnesium disorders]

Extracellular content in magnesium represents about 1% of total body content, of which plasma magnesium is thus a poor reflect. Hypomagnesaemia is defined by a value lesser than 0.65mmol/L. Its incidence in hospitalized patients ranges between 10 and 15%. Identification of the physiopathology of hypomagnesaemia relies first upon concomitant measurement of plasma and urinary magnesium concentration. Daily magnesium excretion lesser than 1mmol/L or EFMg lesser than 1% sign extra renal origin, due to either low magnesium intake, low intestinal absorption of magnesium or derivation of extracellular magnesium toward bone, such as in bone reparation process after hyperparathyroidism surgery. Daily magnesium excretion higher than 2mmol/L concomitant to hypomagnesaemia indicates native or acquired renal loss of magnesium. Congenital renal and extra-renal losses of magnesium are mainly related to rare monogenic disease, and are inconstantly associated with a renal loss of sodium, potassium and calcium. Recent progress in the genetics of this rare diseases have greatly improved the knowledge about proteins involved in intestinal abortion, renal renal tubular re-absorption of magnesium and its regulations. Hypermagnesemia is a rarer metabolic disorder than hypomagnesemia (about 5% of hospitalized patients). Asymptomatic below 2mmol/L, it progressively alters neuromuscular transmission, autonomic sympathic activity and cardiac conduction, with vital risk above 7mol/L. It is due to acute magnesium input into extracellular volume most often associated with a decrease in glomerular filtration rate, limiting the high physiological ability to excrete magnesium input.

Effect of oral magnesium supplementation on measures of airway resistance and subjective assessment of asthma control and quality of life in men and women with mild to moderate asthma: a randomized placebo controlled trial

BACKGROUND

Epidemiological data shows low dietary magnesium(Mg) may be related to incidence and progression of asthma.

OBJECTIVE

To determine if long term(6.5 month) treatment with oral Mg would improve asthma control and increase serum measures of Mg status in men and women with mild-to-moderate asthma.

SUBJECTS

55 males and females aged 21 to 55 years with mild to moderate asthma according to the 2002 National Heart, Lung, and Blood Institute(NHLBI) and Asthma Education and Prevention Program(NAEPP) guidelines and who used only beta-agonists or inhaled corticosteroids(ICS) as asthma medications were enrolled.

DESIGN

Subjects were randomly assigned to consume 340 mg(170 mg twice a day) of Mg or a placebo for 6.5 months.

MEASUREMENTS

Multiple measures of Mg status including serum, erythrocyte, urine, dietary, ionized and IV Mg were measured.

OBJECTIVE

markers of asthma control were: methacholine challenge test(MCCT) and pulmonary function test(PFT) results. Subjective validated questionnaires on asthma quality of life(AQLQ) and control(ACQ) were completed by participants. Markers of inflammation, including c-reactive protein(CRP) and exhaled nitric oxide(eNO) were determined.

RESULTS

The concentration of methacholine required to cause a 20% drop in forced expiratory volume in in minute(FEV(1)) increased significantly from baseline to month 6 within the Mg group. Peak expiratory flow rate(PEFR) showed a 5.8% predicted improvement over time(P = 0.03) in those consuming the Mg. There was significant improvement in AQLQ mean score units(P < 0.01) and in overall ACQ score only in the Mg group(P = 0.05) after 6.5 months of supplementation. Despite these improvements, there were no significant changes in any of the markers of Mg status.

CONCLUSION

Adults who received oral Mg supplements showed improvement in objective measures of bronchial reactivity to methacholine and PEFR and in subjective measures of asthma control and quality of life.

Multiple Measures of Magnesium Status Are Comparable in Mild Asthma and Control Subjects

Magnesium (Mg) may be a significant factor in asthma management. There is debate about how to best assess Mg status. We evaluated multiple indices of Mg status and lung function in 52 people with mild to moderate asthma and 47 controls. Mg measures included serum total, ionized and erythrocyte Mg, intravenous Mg load retention and dietary recall. Methacholine challenge and pulmonary function tests were used to assess diagnosis and severity of asthma. Mg status was similar in asthma and controls, and was not correlated to lung function. Total serum Mg closely reflected ionized Mg and offers a useful clinical diagnostic monitor.

Update on the assessment of magnesium status

Magnesium (Mg) is the fourth most abundant mineral in the body and the most abundant intracellular divalent cation, with essential roles in many physiological functions. Consequently, the assessment of Mg status is important for the study of diseases associated with chronic deficiency. In spite of intense research activities there is still no simple, rapid, and accurate laboratory test to determine total body Mg status in humans. However, serum Mg < 0.75 mmol/l is a useful measurement for severe deficiency, and for values between 0.75 and 0.85 mmol/l a loading test can identify deficient subjects. The loading test seems to be the gold standard for Mg status, but is unsuitable in patients with disturbed kidney and intestinal functions when administered orally. There is also a need to reach a consensus on a standardized protocol in order to compare results obtained in different clinical units. Other cellular Mg measurements, such as total or ionized Mg, frequently disagree and more research and systematic evaluations are needed. Muscle Mg appears to be a good marker, but biopsies limit its usefulness, as is the case with bone Mg, the most important but heterogeneous Mg compartment. The development of new and non invasive techniques such as nuclear magnetic resonance (NMR) may provide valuable tools for routinely analysing ionized Mg in tissues. With the development of molecular genetics techniques, the recent discovery of Transient Receptor Potential Melastatin channels offers new possibilities for the sensitive and rapid evaluation of Mg status in humans.

Intravenous magnesium sulfate with and without EDTA as a magnesium load test-is magnesium deficiency widespread?

Serum/plasma measurements do not reflect magnesium deficits in clinical situations, and magnesium load tests are used as a more accurate method to identify magnesium deficiency in a variety of disease states as well as in subclinical conditions. The objective of this study was to determine if people are indeed magnesium deficient or if the apparent magnesium deficiency is due to the composition of the infusate used in the load test. Magnesium load tests were performed on seven patients using three different Mg solution infusions-a Mg-EDTA (ethylene diamine tetraacetic acid)-nutrient cocktail used in EDTA chelation therapy containing several components including vitamins and minerals, and the same cocktail without EDTA and an infusion of an identical amount of magnesium in normal saline solution. There was no significant difference in the amount of magnesium retained in the 24 h after infusion among the three infusates. All infusates resulted in very high magnesium retention compared to previous published magnesium load studies. Magnesium deficiency may be widespread, and the relationship of Mg deficiency to related diseases requires further study.

Diuretic-related side effects: development and treatment

Diuretics are important therapeutic tools. First, they effectively reduce blood pressure and have been shown in numerous hypertension clinical trials to reduce both cardiovascular and cerebrovascular morbidity and mortality. In addition, their use has been equally effective in controlling cardiovascular events as angiotensin-converting enzyme inhibitors or calcium channel blockers. Diuretics are currently recommended by the Seventh Report of the Joint National Commission on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure report as first-line therapy for the treatment of hypertension. In addition, they remain an important aspect of congestive heart failure treatment in that they improve the congestive symptomatology, which typifies the more advanced stages of congestive heart failure. This article reviews the commonly encountered side effects with the various diuretic classes. Where indicated, the mechanistic basis and treatment of such side effects is further discussed.

Magnesium Treatment of Primary Alcohol-Dependent Patients During Subacute Withdrawal: An Open Pilot Study With Polysomnography

BACKGROUND

Sleep electroencephalogram alterations and insomnia complaints persist after alcohol withdrawal in dependent patients and are considered strong predictors of relapse. Although disturbances of magnesium household due to alcohol consumption are well known, the relationship of magnesium metabolism and sleep disturbances has not been investigated in this patient group. We conducted an open pilot study to evaluate the effects of magnesium treatment on the sleep of primary alcohol-dependent patients during subacute withdrawal.

METHODS

Patients were treated with 30 mmol magnesium daily over 4 weeks. Eleven of the 14 included patients were evaluated. Patients were free of any kind of psychotropic medication or other substances known to influence sleep. Polysomnographic recordings with monitoring of periodic leg movements in sleep (PLMS) were performed for two consecutive nights 2 weeks after acute withdrawal (baseline) and 4 weeks later at the end of the treatment period. After the baseline polysomnography, patients were investigated by the magnesium loading test to verify magnesium depletion.

RESULTS

We found a significant decrease of sleep onset latency from 40.6 to 21.7 min (p = 0.03) and a significant improvement of subjective sleep quality, as assessed by the Pittsburgh Sleep Quality Index, from 8.1 to 5.8 (p = 0.05) during magnesium treatment. Changes in PLMS indices revealed two subgroups of patients: one with an increase of PLMS from 30.7 to 39.4 per hour of sleep (n = 4) and the other one with a decrease of PLMS from 8.9 to 2.1 per hour of sleep (p = 0.04). Patients with PLMS decreases seemed to have a more favorable prognosis: total sleep time, gamma-glutamyltransferase, carbohydrate-deficient transferrin, and Beck Depression Inventory scores improved significantly during treatment in this group. The magnesium loading test revealed a magnesium deficiency in only one patient, five patients showed normal retention values, and the remaining five patients had an increased magnesium excretion, indicating a possible continued renal magnesium loss during abstinence.

CONCLUSIONS

The results of this study should be interpreted with caution, because no control group with placebo was investigated. Both subjective and, partly, objective parameters of sleep improved during the 4-week study period. Further research is needed to clarify the relationship of magnesium metabolism and sleep alterations.

Genetics of hereditary disorders of magnesium homeostasis

Magnesium plays an essential role in many biochemical and physiological processes. Homeostasis of magnesium is tightly regulated and depends on the balance between intestinal absorption and renal excretion. During the last decades, various hereditary disorders of magnesium handling have been clinically characterized and genetic studies in affected individuals have led to the identification of some molecular components of cellular magnesium transport. In addition to these hereditary forms of magnesium deficiency, recent studies have revealed a high prevalence of latent hypomagnesemia in the general population. This finding is of special interest in view of the association between hypomagnesemia and common chronic diseases such as diabetes, coronary heart disease, hypertension, and asthma. However, valuable methods for the diagnosis of body and tissue magnesium deficiency are still lacking. This review focuses on clinical and genetic aspects of hereditary disorders of magnesium homeostasis. We will review primary defects of epithelial magnesium transport, disorders associated with defects in Ca(2+)/ Mg(2+) sensing, as well as diseases characterized by renal salt wasting and hypokalemic alkalosis, with special emphasis on disturbed magnesium homeostasis.

Oral magnesium load test in patients with migraine

OBJECTIVE

To determine whether migraineurs may have a systemic deficiency of magnesium.

BACKGROUND

Magnesium deficiency has been shown to play a potential role in the pathogenesis of migraine, but there are no data on total body magnesium status in migraineurs.

METHODS

An oral magnesium load test was performed by giving 3000 mg of magnesium lactate during a 24-hour interictal period to 20 patients with migraine (15 women and 5 men; mean age, 37.9 years) and 20 healthy volunteers (16 women and 4 men; mean age, 39.6 years). Baseline and postload magnesium concentrations were determined from serum and 24-hour urine specimens.

RESULTS

There was no significant difference between the groups in the baseline serum and urine magnesium concentrations, although the latter tended to be lower (P = .064) in the migraine group. The postload magnesium concentrations were significantly higher within both the migraine (P < .0001 and P < .0001) and the control (P = .0009 and P < .0001) groups compared to the baseline values. After loading, the 24-hour urinary magnesium excretions were significantly lower (P = .0007) in the patients with migraine than in the controls, but serum values did not differ.

CONCLUSIONS

Magnesium retention occurs in patients with migraine after oral loading, suggesting a systemic magnesium deficiency.

Inherited disorders of renal magnesium handling

The genetic basis and cellular defects of a number of primary magnesium wasting diseases have been elucidated over the past decade. This review correlates the clinical pathophysiology with the primary defect and secondary changes in cellular electrolyte transport. The described disorders include (1) hypomagnesemia with secondary hypocalcemia, an earlyonset, autosomal-recessive disease segregating with chromosome 9q12-22.2; (2) autosomal-dominant hypomagnesemia caused by isolated renal magnesium wasting, mapped to chromosome 11q23; (3) hypomagnesemia with hypercalciuria and nephrocalcinosis, a recessive condition caused by a mutation of the claudin 16 gene (3q27) coding for a tight junctional protein that regulates paracellular Mg(2+) transport in the loop of Henle; (4) autosomal-dominant hypoparathyroidism, a variably hypomagnesemic disorder caused by inactivating mutations of the extracellular Ca(2+)/Mg(2+)-sensing receptor, CASR: gene, at 3q13.3-21 (a significant association between common polymorphisms of the CASR: and extracellular Mg(2+) concentration has been demonstrated in a healthy adult population); and (5) Gitelman syndrome, a recessive form of hypomagnesemia caused by mutations in the distal tubular NaCl cotransporter gene, SLC12A3, at 16q13. The basis for renal magnesium wasting in this disease is not known. These inherited conditions affect different nephron segments and different cell types and lead to variable but increasingly distinguishable phenotypic presentations. No doubt, there are in the general population other disorders that have not yet been identified or characterized. The continued use of molecular techniques to probe the constitutive and congenital disturbances of magnesium metabolism will increase the understanding of cellular magnesium transport and provide new insights into the way these diseases are diagnosed and managed.