Magnesium deficiency. Etiology and clinical spectrum

Associations of Serum Magnesium with Brain Morphology and Subclinical Cerebrovascular Disease: The Atherosclerosis Risk in Communities-Neurocognitive Study

Circulating magnesium has been associated with a lower risk of dementia, but the physiologic effects by which magnesium may prevent neurological insults remain unclear. We studied 1466 individuals (mean age 76.2 ± 5.3, 28.8% black, 60.1% female) free of prevalent stroke, with measured serum magnesium and with available MRI scans obtained in 2011–2013, participating in the Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS). Cross-sectional differences in frontal, temporal, parietal, and occipital lobe volume, along with deep grey matter, total brain, and white matter hyperintensity volume across serum magnesium (categorized into quintiles and per standard deviation increases) were assessed using multiple linear regression. We also examined associations of magnesium with the prevalence of cortical, subcortical, and lacunar infarcts using multiple logistic regression. After adjusting for demographics, biomarkers, medications, and cardiometabolic risk factors, higher circulating magnesium was associated with greater total brain volume and frontal, temporal, and parietal lobe volumes (volumes 0.14 to 0.19 standard deviations higher comparing Q5 to Q1). Elevated magnesium was also associated with lower odds of subcortical infarcts (OR (95%CI): 0.44 (0.25, 0.77) comparing Q5 to Q1) and lacunar infarcts (OR (95%CI): 0.40 (0.22, 0.71) comparing Q5 to Q1). Elevated serum magnesium was cross-sectionally associated with greater brain volumes and lower odds of subclinical cerebrovascular disease, suggesting beneficial effects on pathways related to neurodegeneration and cerebrovascular damage. Further exploration through prospective analyses is needed to assess increasing circulating magnesium as a potential neuroprotective intervention.

Associations Between Serum Magnesium Concentrations and Polycystic Ovary Syndrome Status: a Systematic Review and Meta-analysis

Magnesium (Mg) is the second most frequent intracellular cation in humans with a critical role in insulin metabolism and glucoregulation. Women with polycystic ovary syndrome (PCOS) often present with insulin resistance and impaired glucoregulatory status; however, their Mg status remains unclear. Therefore, we aimed to conduct a systematic review and meta-analysis to evaluate serum Mg concentration in women with PCOS and compare it with that of controls without PCOS. Online databases of PubMed, Scopus, Cochrane Library, and ISI Web of Science were searched for studies evaluating the relationship between Mg concentrations and PCOS status until October 2019. Pooled weighted mean differences (WMDs) of serum Mg levels were calculated using random effects models. A total of eight studies (10 arms; n = 2026 women) were included. Pooled effect sizes, expressed as WMD and 95% CI, revealed decreased serum Mg concentrations in women with PCOS compared with controls (- 0.09 (- 0.17, - 0.02) mmol/L; P = 0.01). However, significant heterogeneity was detected across the studies (I ² = 98.0%, P < 0.001). Despite the classification of studies based on baseline BMI classes, we did not detect the potential source of the observed heterogeneity. Subgroup analysis showed that overweight and obese women (BMI ≥ 25 kg/m², 0.07 mmol/L (- 0.14, - 0.01); P = 0.02) with PCOS had lower magnesium concentrations than normal women (BMI < 25 kg/m², - 0.11 (- 0.25, 0.04) mmol/L; P = 0.14) compared with the control group. Serum Mg concentrations appear to be declined in overweight or obese women with PCOS, which may warrant screening and management of Mg status in this clinical population. High-quality studies are needed to elucidate the relationship between Mg concentrations and the development of PCOS.

Prevalence and risk factors of long-term proton pump inhibitors-associated hypomagnesemia: a cross-sectional study in hospitalized patients

Proton pump inhibitors (PPI)-related hypomagnesemia is a potentially life-threatening adverse event first described in 2006. PPIs are widely used in the general population. Information regarding prevalence and risk factors is scarce. We conducted a cross-sectional study in inpatients to evaluate prevalence and associated factors with hypomagnesemia in chronic PPIs users. This is a cross-sectional study of hospitalized adult patients with chronic use of PPIs from January 01, 2012, to December 31, 2018. Chronic use was defined as taking PPIs at least 6 months before hospital admittance. Data were collected from informatized medical records from a University Hospital (Hospital Italiano de Buenos Aires). Hypomagnesemia was defined as a value equal to or less than 1.7 mg/dl. The first hospitalization measurement was retrieved. Thirty-six percent of patients (95% CI 30-43) with chronic PPI use presented hypomagnesemia at admission. Patients with hypomagnesemia presented a higher prevalence of chronic kidney disease (18.6% vs 8%, p < 0.05), more use of oral magnesium supplementation (20.9% vs 8%, p < 0.05), use of corticosteroids (32.6% vs 19.3%, p = 0.06) and calcineurin inhibitors (17.4% vs 6.7%, p < 0.05). Regarding laboratory findings, they presented lower hematocrit (28.7% vs 32.8%, p < 0.05), phosphatemia (3 mg/dl vs 3.4 mg/dl, p < 0.05), natremia (135 mg/dl vs 136 mg/dl, p < 0.05) and albumin levels (2.8 g/dl vs 3.2 g/dl p < 0.05) when compared to those who presented normomagnesemia. Hypocalcemia was more frequent among patients with hypomagnesemia (57% vs 38.7%, p < 0.05). In the multivariate analysis, hyponatremia, decreasing levels of hematocrit (odds ratio, OR 0.93-CI 95% 0.88-0.98) and malignant bone compromise (OR 2.83-CI 95% 1.04-7.7) were associated with hypomagnesemia. Adult patients with long-term use of PPIs have a high prevalence of hypomagnesemia. Increasing age, female sex, concomitant use of drugs that impair tubular function and chronic kidney disease may enhance this phenomenon. Anemia, hyponatremia and malignant bone compromise were associated factors with PPIs-related hypomagnesemia.

Is there a correlation between hypomagnesemia linked to long-term proton pump inhibitor use and the active agent?

BACKGROUND

One of the electrolyte disorders considered to be linked to proton pump inhibitors (PPI) use is hypomagnesemia. The aim of this study was to assess the incidence of hypomagnesemia linked to long-term PPI use and the correlation with active agents.

METHODS

The study included 305 patients aged over 18 years with PPI use of 1 year or longer and attending the internal diseases clinic for any reason from April 2019 to December 2019. A survey study was performed about the demographic characteristics and PPI use of patients. Laboratory parameters, such as the hemogram, magnesium, phosphorus, calcium and vitamin B12 concentrations were recorded. Magnesium concentrations were measured by a colorimetric method.

RESULTS

Of the patients 140 (45.9%) were female and 165 (54.1%) were male. The most commonly used PPI active agent was pantoprazole. The duration of PPI use varied from 1-25 years with a mean of 4.31 ± 4.52 years. Of the patients 51.5% reported no medication side effects. The most commonly observed side effect was constipation (n = 98, 32.1%). The mean magnesium concentration was 1.95 ± 0.02 mg/dL. Hypomagnesemia was identified in 65 (21.3%) patients and the incidence increased as age and duration of use increased. Patients using omeprazole had significantly lower magnesium levels compared to patients using pantoprazole, rabeprazole, esomeprazole and lansoprazole.

CONCLUSION

In light of the data obtained it was concluded that hypomagnesemia linked to PPI use is associated with the type of PPI. While patients using rabeprazole had the lowest rates, those using omeprazole had significantly higher rates of hypomagnesemia. Additionally, there was a proportional correlation between age and duration of use with the risk of development of hypomagnesemia.

Magnesium in Aging, Health and Diseases

Several changes of magnesium (Mg) metabolism have been reported with aging, including diminished Mg intake, impaired intestinal Mg absorption and renal Mg wasting. Mild Mg deficits are generally asymptomatic and clinical signs are usually non-specific or absent. Asthenia, sleep disorders, hyperemotionality, and cognitive disorders are common in the elderly with mild Mg deficit, and may be often confused with age-related symptoms. Chronic Mg deficits increase the production of free radicals which have been implicated in the development of several chronic age-related disorders. Numerous human diseases have been associated with Mg deficits, including cardiovascular diseases, hypertension and stroke, cardio-metabolic syndrome and type 2 diabetes mellitus, airways constrictive syndromes and asthma, depression, stress-related conditions and psychiatric disorders, Alzheimer's disease (AD) and other dementia syndromes, muscular diseases (muscle pain, chronic fatigue, and fibromyalgia), bone fragility, and cancer. Dietary Mg and/or Mg consumed in drinking water (generally more bioavailable than Mg contained in food) or in alternative Mg supplements should be taken into consideration in the correction of Mg deficits. Maintaining an optimal Mg balance all through life may help in the prevention of oxidative stress and chronic conditions associated with aging. This needs to be demonstrated by future studies.

Nutrition in alcohol-related liver disease: Physiopathology and management

Malnutrition encompassing both macro- and micro-nutrient deficiency, remains one of the most frequent complications of alcohol-related liver disease (ArLD). Protein-energy malnutrition can cause significant complications including sarcopenia, frailty and immunodepression in cirrhotic patients. Malnutrition reduces patient’s survival and negatively affects the quality of life of individuals with ArLD. Moreover, nutritional deficit increases the likelihood of hepatic decompensation in cirrhosis. Prompt recognition of at-risk individuals, early diagnosis and treatment of malnutrition remains a key component of ArLD management. In this review, we describe the pathophysiology of malnutrition in ArLD, review the screening tools available for nutritional assessment and discuss nutritional management strategies relevant to the different stages of ArLD, ranging from acute alcoholic hepatitis through to decompensated end stage liver disease.

Magnesium Preparations in Psychiatry, Addiction Medicine, Neurology and General Medicine (Part I. History)

The use of magnesium preparations in medicine has a long history. According to some sources, first attempts by humans to consume magnesium- and calcium-rich minerals orally, presumably for medicinal purposes, could have occurred even in prehistoric times. First attempts to use natural magnesium-calcium alkaline materials to increase the bioavailability of the alkaloids of some psychoactive plants, such as betel, tobacco, and coca, also date back to prehistoric times.Later, several ancient authors, in particular, Hippocrates II, Claudius Galen and Soran of Ephesus, have described the profound laxative effect of sea salt and of crushed dolomite, as well as a positive effect on the psyche of drinking mineral waters from sources that were found by modern scientists to be rich in magnesium, lithium and bromine. The laxative effect of mineral waters from some sources rich in magnesium, or of salts that were extracted from such sources was known in the Middle Ages. Later, Paracelsus discovered that these salts could be useful not only as a laxative, but also as a sedative.In 1707, Massimiliano Valentini first obtained magnesium oxide, which immediately found its use in medicine, as an antacid, as a mild laxative and skin powder. In 1926, Jacques Leroy was the first to prove the vital importance of magnesium for the physiology of animals.In this article, we thoroughly review the history of the medicinal use of magnesium preparations and the history of studies of biological role of magnesium, from antiquity to modern times.

Biomarkers in Sports and Exercise: Tracking Health, Performance, and Recovery in Athletes

Lee, EC, Fragala, MS, Kavouras, SA, Queen, RM, Pryor, JL, and Casa, DJ. Biomarkers in sports and exercise: tracking health, performance, and recovery in athletes. J Strength Cond Res 31(10): 2920–2937, 2017—Biomarker discovery and validation is a critical aim of the medical and scientific community. Research into exercise and diet-related biomarkers aims to improve health, performance, and recovery in military personnel, athletes, and lay persons. Exercise physiology research has identified individual biomarkers for assessing health, performance, and recovery during exercise training. However, there are few recommendations for biomarker panels for tracking changes in individuals participating in physical activity and exercise training programs. Our approach was to review the current literature and recommend a collection of validated biomarkers in key categories of health, performance, and recovery that could be used for this purpose. We determined that a comprehensive performance set of biomarkers should include key markers of (a) nutrition and metabolic health, (b) hydration status, (c) muscle status, (d) endurance performance, (e) injury status and risk, and (f) inflammation. Our review will help coaches, clinical sport professionals, researchers, and athletes better understand how to comprehensively monitor physiologic changes, as they design training cycles that elicit maximal improvements in performance while minimizing overtraining and injury risk.

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.

SIDS-CDF Hypothesis Revisited: Cause vs. Contributing Factors

The sudden infant death syndrome (SIDS)–critical diaphragm failure (CDF) hypothesis was first published by Siren and Siren in 2011 (1). Since its publication, the hypothesis has continued to generate interest and several colleagues have contributed perspectives and insights to it (2–5). The basic premise of the hypothesis is that the diaphragm is a vital organ that must continuously generate adequate force to maintain ventilation, and that CDF is a terminal event and the cause of death in SIDS. I have argued in two follow-up articles that all SIDS factors either increase the workload of the respiratory muscles, the diaphragm being the primary muscle affected, or reduce its force generating capacity (6, 7). The SIDS–CDF hypothesis posits that SIDS has many contributing factors but only one cause, namely, the failure of the vital respiratory pump. There are several known SIDS factors, such as the prone sleeping position, non-lethal infections, deep sleep, gestational prematurity, low birth weight, cigarette smoke, male gender, and altitude, but of these, some such as the prone sleeping position more significantly both impact diaphragm function and correlate with SIDS. However, SIDS cases are multifactorial and as such can be caused by different combinations of factors. An infection combined with a prone sleeping position and elevated room temperature could lead to SIDS, whereas in other circumstances, low birth weight, cigarette smoke, prone sleeping position, and altitude could result in CDF and SIDS. The SIDS–CDF hypothesis also posits that SIDS does not have a congenital or genetic origin, and that efforts to identify significant genetic anomalies in SIDS victims are unlikely to be successful (8–11).

Prevalence and predictive factors of preoperative hypomagnesaemia among adult surgical patients in a large tertiary hospital in Ghana

Background

Magnesium is the second most abundant intracellular cation and a co-factor in several reactions involved in the formation and usage of adenosine triphosphate and nucleic acid synthesis. Magnesium deficiency may be as high as 65 % in patients admitted to a medical Intensive Care Unit (ICU). Significant and potentially fatal conditions have been attributed to hypomagnesaemia and it has also been associated with poor prognosis and increased mortality in the critically ill. The study aimed to determine the prevalence and identify the predictive factors of preoperative hypomagnesaemia in adult surgical patients who require an emergency laparotomy.

Methods

This was a hospital based prospective study conducted at the Korle-Bu teaching hospital. General surgical patients between the ages of eighteen and seventy years with a preoperative diagnosis which required emergency laparotomy for management were consecutively enrolled into the study. A total of 102 patients were enrolled in the study. Preoperative total serum magnesium and serum potassium were determined.

Data was summarised utilising simple descriptive statistics (i.e., proportions, ratios and percentages). The Chi-square test was used to determine significant differences or associations between categorical variables, Pearson’s correlation coefficient was used to determine the relationship between continuous variables and predictive factors were determined by multiple regression. Analysis was done in SPSS version 16.

Results

The mean serum total magnesium and potassium were 0.66 ± 0.20 mmol/L and 3.79 ± 0.65 mmol/L respectively. The prevalence of preoperative hypomagnesaemia was found to be 68.0 %. Multiple logistic regression found only hypokalaemia to be a predictive factor (p-value of 0.001, odd’s ratio of 9.21 and a confidence interval of 2.42–35.09).

Conclusion

The prevalence of preoperative hypomagnesaemia was high (68.0 %) with hypokalaemia the only predictive factor. Hypokalaemic patients requiring emergency laparotomy are nine times more likely to develop hypomagnesaemia as compared to patients who were not hypokalaemic.

Changes in serum magnesium concentration after use of a proton pump inhibitor in patients undergoing percutaneous coronary intervention

Background

Although cross-sectional studies have suggested a relationship between proton pump inhibitor (PPI) use and hypomagnesemia, no large-scale cohort study has been conducted to date. Here, we examined the changes in serum magnesium levels in response to PPI use. We hypothesized that PPI use might change the serum magnesium concentration.

Methods

Of the 2,892 patients hospitalized for percutaneous coronary intervention between January 2007 and May 2012, 1,076 patients with normal baseline (1.6–2.5 mg/dL) and follow-up serum magnesium concentrations were enrolled. These patients were divided into two groups: the PPI group and the control group.

Results

The mean follow-up period was 9.51 ± 2.94 months. The incidence of hypomagnesemia (< 1.6 mg/dL) was 0.4% (3/834) in the PPI group and 0.4% (1/242) in the control group (P = 0.904). The change in magnesium levels did not differ between the two groups, and this result was maintained in the analysis of covariance after adjusting for confounding factors (P = 0.381). Moreover, magnesium levels did not significantly differ between the long-term (duration of use ≥ 12 months, n = 71) and short-term PPI groups (duration of use < 12 months, n = 763), and the control group (n = 242; P = 0.620). The effect of PPI use on change in serum magnesium concentration was affected by the use of multiple diuretics (−0.01 ± 0.25 mg/dL; P = 0.025), although a single diuretic use with PPI did not alter the change in magnesium level (0.12 ± 0.27 mg/dL).

Conclusion

Changes in magnesium levels might be subtle after PPI use in patients with normal baseline magnesium values.

Hypomagnesemia: a clinical perspective

Although magnesium is involved in a wide spectrum of vital functions in normal human physiology, the significance of hypomagnesemia and necessity for its treatment are under-recognized and underappreciated in clinical practice. In the current review, we first present an overview of the clinical significance of hypomagnesemia and normal magnesium metabolism, with a focus on renal magnesium handling. Subsequently, we review the literature for both congenital and acquired hypomagnesemic conditions that affect the various steps in normal magnesium metabolism. Finally, we present an approach to the routine evaluation and suggested management of hypomagnesemia.

Effects of proton pump inhibitors and electrolyte disturbances on arrhythmias

Several case reports have been written regarding the relationship between the use of proton pump inhibitors (PPI) and hypomagnesemia. Some of these reported cases have electrocardiogram abnormalities where electrolytes deficiencies were the contributing factor for these events. This study investigates the correlation between different arrhythmias and the use of PPI and hypomagnesaemia incidence. Four-hundred and twenty-one patients admitted to the critical care unit with unstable angina, non-ST elevation myocardial infarction, and ST-elevation myocardial infarction were included in this study. One-hundred and eighty-four patients (43.8%) received PPI and 237 patients (51.16%) did not, magnesium levels were low (<1.8 mg/dL) in 95 patients (22.5%), and 167 patients (39.6%) developed arrhythmias. The P-values for the regression coefficient association for the use of PPI and the level of magnesium were P = 1.31e(-29) and P = 8e(-102), respectively. The P-values indicate that there is a statistically significant association between the PPI use, magnesium levels, and the occurrence of cardiovascular events, with a strong correlation factor of 0.817. Patients receiving PPIs should be followed closely for magnesium deficiency, especially if they experience acute cardiovascular events, because this may contribute to worsening arrhythmias and further complications.

Proton-pump inhibitor use is associated with low serum magnesium concentrations

Although case reports link proton-pump inhibitor (PPI) use and hypomagnesemia, no large-scale studies have been conducted. Here we examined the serum magnesium concentration and the likelihood of hypomagnesemia (<1.6 mg/dl) with a history of PPI or histamine-2 receptor antagonist used to reduce gastric acid, or use of neither among 11,490 consecutive adult admissions to an intensive care unit of a tertiary medical center. Of these, 2632 patients reported PPI use prior to admission, while 657 patients were using a histamine-2 receptor antagonist. PPI use was associated with 0.012 mg/dl lower adjusted serum magnesium concentration compared to users of no acid-suppressive medications, but this effect was restricted to those patients taking diuretics. Among the 3286 patients concurrently on diuretics, PPI use was associated with a significant increase of hypomagnesemia (odds ratio 1.54) and 0.028 mg/dl lower serum magnesium concentration. Among those not using diuretics, PPI use was not associated with serum magnesium levels. Histamine-2 receptor antagonist use was not significantly associated with magnesium concentration without or with diuretic use. The use of PPI was not associated with serum phosphate concentration regardless of diuretic use. Thus, we verify case reports of the association between PPI use and hypomagnesemia in those concurrently taking diuretics. Hence, serum magnesium concentrations should be followed in susceptible individuals on chronic PPI therapy.

Proton pump inhibitor-induced hypomagnesemia: A new challenge

Proton pump inhibitors (PPIs) are commonly used in clinical practice for the prevention and treatment of peptic ulcer, gastritis, esophagitis and gastroesophageal reflux. Hypomagnesemia has recently been recognized as a side effect of PPIs. Low magnesium levels may cause symptoms from several systems, some of which being potentially serious, such as tetany, seizures and arrhythmias. It seems that PPIs affect the gastrointestinal absorption of magnesium. Clinicians should be vigilant in order to timely consider and prevent or reverse hypomagnesemia in patients who take PPIs, especially if they are prone to this electrolyte disorder.

Tetany: A diagnostic dilemma

Tetany is a disorder of increased neuronal excitability usually associated with hypocalcemia. We report a patient with typical tetanic cramps and carpopedal spasm in the postoperative period, despite normal serum concentrations of calcium, which responded to intravenous infusion of calcium.

Hypocalcaemia and chronic alcohol intoxication: transient hypoparathyroidism secondary to magnesium deficiency

The authors report the observation of an alcoholic patient admitted for tetanic manifestations, in whom severe hypocalcaemia associated with hyperphosphatemia were suggestive of hypoparathyroidism. Administration of magnesium supplementation alone improved the clinical features and led to the correction of the calcium abnormalities. The mechanisms of hypomagnesemia in alcohol intoxication are reviewed as well as the links with hypocalcaemia.

Iron accumulation in tissues of magnesium-deficient rats with dietary iron overload

The mineral imbalances in magnesium-deficient rats with dietary iron overload were studied. Forty-four male Wistar rats were divided into six groups and fed six diets, two by three, fully crossed: magnesium adequate or deficient, and iron deficient, adequate, or excess. The concentrations of iron, magnesium, calcium, and phosphorus in tissues of the rats were measured. The results were as follows: (1) The excess iron intake reinforced the iron accumulation in liver and spleen of magnesium deficient rats; (2) The saturation of iron binding capacity was enormously elevated in the magnesium deficient rats fed excess iron; and (3) Dietary iron deprivation diminished the degree of calcium deposition in kidney of magnesium deficient rats. These results suggest that magnesium-deprived rats have abnormal iron metabolism losing homeostatic regulation of plasma iron, and magnesium deficient rats with dietary iron overload may be used as an experimental hemochromatosis model.

Magnesium deficiency as a cause of acute intractable seizures

Clinical and experimental investigations have shown that magnesium depletion causes a marked irritability of the nervous system, eventually resulting in epileptic seizures. Although magnesium deficiency as a cause of epilepsy is uncommon, its recognition and correction may prove life-saving. Two case reports are presented which emphasize the importance of recognizing hypomagnesaemia in patients with acute intractable seizures.

Ventricular extrasystoles during thiazide treatment: substudy of MRC mild hypertension trial

One short term and one long term study of the relation between ventricular extrasystoles and thiazide treatment were carried out during the Medical Research Council's mild hypertension trial. In the short term study 110 patients were randomly assigned to one of three treatment groups, bendrofluazide with or without potassium supplements, or placebo. They were studied before starting treatment and nine to 10 weeks later while still taking their randomly assigned drugs. No significant increase in the number of ventricular extrasystoles was associated with short term thiazide treatment, although serum potassium concentrations changed as expected. In the long term study 214 patients who had completed an average of two years' treatment with randomly assigned bendrofluazide or a placebo were studied while continuing to take their trial tablets; the 214 included 20 people who had been randomised at entry to the bendrofluazide group and who had a subsequent history of hypokalaemia. These 20 patients were studied before and after being further randomised to two groups, one continuing treatment without change and one continuing with bendrofluazide and also taking potassium supplements. Counts of ventricular extrasystoles were significantly higher (p = 0.025) in those receiving long term thiazide treatment than in their controls; however, there was no significant association between the number of ventricular extrasystoles and serum potassium concentrations in this group, although the correlation between number of extrasystoles and serum urate concentrations was significant (p = 0.035). Pooled data for both studies showed a highly significant correlation between number of ventricular extrasystoles, and serum potassium concentrations (r = -0.185; p = 0.003), but the correlation with serum urate concentrations was of similar strength (r = 0.178; p = 0.004). These biochemical changes may be acting merely as markers of thiazide intake, and the explanation of the association between thiazide treatment and ventricular extrasystolic activity therefore remains uncertain.