Hyperkalemia and hyporeninemic hypoaldosteronism

Use of Fludrocortisone for Hyperkalemia in Chronic Kidney Disease Not Yet on Dialysis

Background

Hyperkalemia is a frequent and potentially lethal complication of chronic kidney disease (CKD). We retrospectively examined the potassium-lowering effect of oral fludrocortisone and its adverse effects in hyperkalemic CKD patients not yet on dialysis.

Methods

Thirty-three patients (23 men and 10 women, ages 69±14 years) were included. To control hyperkalemia at the outpatient clinic, twenty-one patients (Group 1) received fludrocortisone (0.05-0.1 mg/day) without changes in angiotensin II receptor blockers (ARBs) and calcium polystyrene sulfonate (CPS), while twelve patients (Group 2) were treated with fludrocortisone in addition to stopping ARBs and/or adding low-dose CPS.

Results

Fludrocortisone was administered for a median of 169 days (interquartile range, 47-445). At the first follow-up after fludrocortisone administration, serum potassium dropped from 6.14±0.32 mEq/L to 4.52±1.06 mEq/L (p<0.001) in Group 1 and from 6.37±0.35 mEq/L to 4.08±0.74 mEq/L (p<0.01) in Group 2. Ten patients in Group 1 and five patients in Group 2 measured serum potassium levels at four outpatient visits before and after fludrocortisone administration, respectively. The frequency of serum potassium ≥6.0 mEq/L decreased from 19/40 (48%) to 2/40 (5%) (p<0.001) in Group 1 and from 11/20 (55%) to 0/20 (0%) (p<0.001) in Group 2. Eleven patients experienced sodium retention-related problems after fludrocortisone administration: 7 with worsening leg edema, 2 with pleural effusions, and 2 with pulmonary edema.

Conclusion

In pre-dialysis CKD patients, fludrocortisone at low doses effectively reduced serum potassium levels; however, sodium retention was a common adverse effect.

The Role of the Endocrine System in the Regulation of Acid-Base Balance by the Kidney and the Progression of Chronic Kidney Disease

Systemic acid-base status is primarily determined by the interplay of net acid production (NEAP) arising from metabolism of ingested food stuffs, buffering of NEAP in tissues, generation of bicarbonate by the kidney, and capture of any bicarbonate filtered by the kidney. In chronic kidney disease (CKD), acid retention may occur when dietary acid production is not balanced by bicarbonate generation by the diseased kidney. Hormones including aldosterone, angiotensin II, endothelin, PTH, glucocorticoids, insulin, thyroid hormone, and growth hormone can affect acid-base balance in different ways. The levels of some hormones such as aldosterone, angiotensin II and endothelin are increased with acid accumulation and contribute to an adaptive increase in renal acid excretion and bicarbonate generation. However, the persistent elevated levels of these hormones can damage the kidney and accelerate progression of CKD. Measures to slow the progression of CKD have included administration of medications which inhibit the production or action of deleterious hormones. However, since metabolic acidosis accompanying CKD stimulates the secretion of several of these hormones, treatment of CKD should also include administration of base to correct the metabolic acidosis.

Evaluating renin and aldosterone levels in children with organic acidemia-therapeutic experience with fludrocortisone

Hyporeninemic hypoaldosteronism has been reported in only a few cases with methylmalonic acidemia (MMA) and has been attributed to the renal involvement. This study aims to investigate renin-aldosterone levels along with the renal functions of the patients with organic acidemia. This is a cross-sectional study conducted in patients with MMA, propionic acidemia (PA), and isovaleric acidemia (IVA). Serum renin, aldosterone, sodium, and potassium levels were measured, and glomerular filtration rates (GFR) were calculated. Comparisons were made between the MMA and non-MMA (PA+IVA) groups. Thirty-two patients (MMA:PA:IVA = 14:13:5) were included. The median GFR was significantly lower in the MMA group than in the non-MMA group (p < 0.001). MMA patients had the highest incidence of kidney damage (71.4%), followed by PA patients (23%), while none of the IVA patients had reduced GFR. GFR positively correlated with renin levels (p = 0.015, r = 0.433). Although renin levels were significantly lower in the MMA group than the non-MMA group (p = 0.026), no significant difference in aldosterone levels was found between the two groups. Hyporeninemic hypoaldosteronism was found in 3 patients with MMA who had different stages of kidney damage, and fludrocortisone was initiated, which normalized serum sodium and potassium levels.  Conclusions: This study, which has the largest number of patients among the studies investigating the renin-angiotensin system in organic acidemias to date, has demonstrated that hyporeninemic hypoaldosteronism is not a rare entity in the etiology of hyperkalemia in patients with MMA, and the use of fludrocortisone is an effective treatment of choice in selected cases. What is Known: • Hyperkalemia may be observed in cases of methylmalonic acidemia due to renal involvement and can be particularly prominent during metabolic decompensation. • Hyporeninemic hypoaldosteronism has been reported to be associated with hyperkalemia in only a few cases of methylmalonic acidemia. What is New: • Hyporeninemic hypoaldosteronism was found in one-fifth of cases with methylmalonic acidemia. • Fludrocortisone therapy leads to the normalization of serum sodium and potassium levels.

Adherence to glucocorticoid replacement therapy in Addison's disease: Association with patients' disease knowledge and quality of life

Little is known about the quality of adherence to glucocorticoid replacement therapy in patients with Addison disease (AD). The aim of this study was to evaluate the quality of glucocorticoid treatment adherence in patients with AD and to assess its association with patients' disease knowledge and quality of life.

METHODS

This is a cross-sectional study including 58 patients with AD. The Girerd questionnaire was used to assess the quality of adherence to glucocorticoid replacement therapy. A questionnaire was specially designed to assess patients' disease knowledge. The AddiQol questionnaire, specific to AD, was used to assess the patients' quality of life. Patients were considered non-adherent if they gave three or fewer than three negative answers to the Girerd questionnaire (score≤3/6).

RESULTS

The mean age of the patients was 48.4±13.3 years (39 women and 19 men). Twenty-seven patients (46%) were non-adherent to glucocorticoid replacement therapy. An age below 48 years, poor adherence to comorbidity treatments, baseline cortisolemia at diagnosis>5μg/dl, history of adrenal crisis, poor knowledge about the disease, BMI<26.7kg/m2, waist circumference<90cm, low systolic blood pressure, fasting blood glucose<0.9g/l, and triglyceride<1g/l were the factors independently associated with non-adherence (respectively ORa [CI 95%]=4.8 [2.8-10.7], 5.0 [3.0-12.2], 2.3 [1.2-6.2], 4.1 [2.0-8.3], 3.9 [1.2-7.2], 3.9 [1.1-6.9], 1.8 [1.1-2.9], 4.8 [2.6-8.2], 2.5 [1.1-5.3], and 2.2 [1.1-5.1]). There was a positive correlation between the disease knowledge questionnaire score and the Girerd score (p=0.02, r=0.31). There was a positive correlation between the AddiQoL score and the Girerd score (p=0.01, r=0.32).

CONCLUSION

Non-adherence to glucocorticoid replacement therapy was common in patients with AD and was associated with more frequent adrenal crisis and poorer quality of life. The quality of treatment adherence was correlated with patients' disease knowledge. Therapeutic education is essential to reduce the frequency of non-adherence, especially among young patients.

Diagnostic predictivity of transtubular potassium gradient for primary hypoadrenocorticism in hyperkalemic dogs: a cross-sectional study

OBJECTIVES

Transtubular potassium gradient has never been evaluated in the diagnosis of primary hypoadrenocorticism in dogs. The objective of this study is to evaluate the diagnostic utility of transtubular potassium gradient for the diagnosis of primary hypoadrenocorticism in dogs with serum K+  > 5.5 mol/L.

MATERIALS AND METHODS

Cross-sectional study including dogs with primary hypoadrenocorticism and dogs with other disease. Differences in signalment and laboratory parameters between groups were assessed by binary logistic regression modelling. Variables significantly associated with primary hypoadrenocorticism were evaluated for their diagnostic accuracy of this condition by receiver operator characteristic curve analysis and by multivariable logistic regression analysis, respectively.

RESULTS

Dogs with primary hypoadrenocorticism (n=39) were significantly younger than hyperkalemic dogs without primary hypoadrenocorticism (n=41). Moreover they had higher serum and urinary concentrations of Na+ and Na+ :K+ , but lower transtubular potassium gradient than hyperkalemic dogs without hypoadrenocorticism. Serum Na+ (sNa+ ) had the highest diagnostic accuracy (area under the curve [AUC]: 0.87, 95% confidence interval, 0.78 to 0.96), followed by the transtubular potassium gradient (AUC: 0.81, 0.72 to 0.91), however the accuracy of the two AUCs was not statistically different. The transtubular potassium gradient-sNa+ additive index (i.e. transtubular potassium gradient+sNa+ /10) had a greater accuracy (AUC: 0.88, 0.79 to 0.94) than transtubular potassium gradient or sNa+ , although it was not statistically superior to the latter. The multivariable logistic regression model showed that transtubular potassium gradient (adjusted odds ratio [aOR]: 0.51, 0.3 to 0.84), sNa+ (aOR: 0.86, 0.78 to 0.95) and spayed female (aOR: 24.96, 2.32 to 267.66) were associated with primary hypoadrenocorticism.

CLINICAL SIGNIFICANCE

Transtubular potassium gradient-sNa+ additive index can contribute to decision-making on diagnosis of primary hypoadrenocorticism in dogs presenting with hyperkalaemia.

ER ribosomal-binding protein 1 regulates blood pressure and potassium homeostasis by modulating intracellular renin trafficking

BACKGROUND

Genome-wide association studies (GWASs) have linked RRBP1 (ribosomal-binding protein 1) genetic variants to atherosclerotic cardiovascular diseases and serum lipoprotein levels. However, how RRBP1 regulates blood pressure is unknown.

METHODS

To identify genetic variants associated with blood pressure, we performed a genome-wide linkage analysis with regional fine mapping in the Stanford Asia-Pacific Program for Hypertension and Insulin Resistance (SAPPHIRe) cohort. We further investigated the role of the RRBP1 gene using a transgenic mouse model and a human cell model.

RESULTS

In the SAPPHIRe cohort, we discovered that genetic variants of the RRBP1 gene were associated with blood pressure variation, which was confirmed by other GWASs for blood pressure. Rrbp1- knockout (KO) mice had lower blood pressure and were more likely to die suddenly from severe hyperkalemia caused by phenotypically hyporeninemic hypoaldosteronism than wild-type controls. The survival of Rrbp1-KO mice significantly decreased under high potassium intake due to lethal hyperkalemia-induced arrhythmia and persistent hypoaldosteronism, which could be rescued by fludrocortisone. An immunohistochemical study revealed renin accumulation in the juxtaglomerular cells of Rrbp1-KO mice. In the RRBP1-knockdown Calu-6 cells, a human renin-producing cell line, transmission electron and confocal microscopy revealed that renin was primarily retained in the endoplasmic reticulum and was unable to efficiently target the Golgi apparatus for secretion.

CONCLUSIONS

RRBP1 deficiency in mice caused hyporeninemic hypoaldosteronism, resulting in lower blood pressure, severe hyperkalemia, and sudden cardiac death. In juxtaglomerular cells, deficiency of RRBP1 reduced renin intracellular trafficking from ER to Golgi apparatus. RRBP1 is a brand-new regulator of blood pressure and potassium homeostasis discovered in this study.

Evolution of Mineralocorticoid Receptor Antagonists in the Treatment of Chronic Kidney Disease Associated with Type 2 Diabetes Mellitus

Chronic kidney disease (CKD) is one of the most frequent complications associated with type 2 diabetes mellitus (T2DM) and is also an independent risk factor for cardiovascular disease. The mineralocorticoid receptor (MR) is a nuclear receptor expressed in many tissue types, including kidney and heart. Aberrant and long-term activation of MR by aldosterone in patients with T2DM triggers detrimental effects (eg, inflammation and fibrosis) in these tissues. The suppression of aldosterone at the early stage of T2DM has been a therapeutic strategy for patients with T2DM-associated CKD. Although patients have been treated with renin-angiotensin system (RAS) blockers for decades, RAS blockers alone are not sufficient to prevent CKD progression. Steroidal MR antagonists (MRAs) have been used in combination with RAS blockers; however, undesired adverse effects have restricted their usage, prompting the development of nonsteroidal MRAs with better target specificity and safety profiles. Recently conducted studies, Finerenone in Reducing Kidney Failure and Disease Progression in Diabetic Kidney Disease (FIDELIO-DKD) and Finerenone in Reducing Cardiovascular Mortality and Morbidity in Diabetic Kidney Disease (FIGARO-DKD), have reported that finerenone, a nonsteroidal MRA, improves both renal and cardiovascular outcomes compared with placebo. In this article, we review the history of MRA development and discuss the possibility of its combination with other treatment options, such as sodium-glucose cotransporter 2 inhibitors, glucagon-like peptide-1 receptor agonists, and potassium binders for patients with T2DM-associated CKD.

Clinical manifestations and associated factors in acquired hypoaldosteronism in endocrinological practice

Introduction

Hypoaldosteronism can be congenital or acquired, isolated or part of primary adrenal insufficiency, and caused by an aldosterone deficit, resistance, or a combination of both. Reduced mineralocorticoid action can induce a decrease in urine K+ and H+ excretion and an increase in urine Na+ excretion, leading to hyperkalemia, and/or hyponatremia, often combined with metabolic acidosis. We aimed to characterize the clinical manifestations of hypoaldosteronism, and their associated factors.

Methods

Retrospective analysis of 112 episodes of hypoaldosteronism diagnosed in 86 adult patients from 2012-2019 by the Endocrinology and Nutrition Department of a tertiary hospital. The frequency of hyperkalemia, hypovolemic hyponatremia (HH) and metabolic acidosis (MA), and their associated factors were evaluated.

Results

Patients had a median age of 77 [65 - 84], 55.4% were male. 94.6% cases showed hyperkalemia, 54.5% HH, and 60.3% MA. The mean serum K+ of all cases was 5.4 ± 0.5 mmol/L, Na+: 132.1 ± 6.3 mmol/L, HCO3: 22.6 ± 3.3 mmol/L. Hypoaldosteronism was isolated in the majority of cases: only 6/112 (5%) had primary adrenal insufficiency. Hypovolemia was associated with hyponatremia and a more florid clinical presentation. HH was associated with a combined presence of aldosterone-lowering and mineralocorticoid resistance factors. MA was associated with the presence of mineralocorticoid resistance factors.

Conclusions

Hypoaldosteronism in adult endocrinological clinical practice is primarily isolated, and acquired. It predisposes not only to the development of hyperkalemia and MA, but also to that of HH. Hypoaldosteronism must be considered in the differential diagnosis of HH with urinary sodium wasting.

The nephropathy of sickle cell trait and sickle cell disease

Sickle cell syndromes, including sickle cell disease (SCD) and sickle cell trait, are associated with multiple kidney abnormalities. Young patients with SCD have elevated effective renal plasma flow and glomerular filtration rates, which decrease to normal ranges in young adulthood and subnormal levels with advancing age. The pathophysiology of SCD-related nephropathy is multifactorial - oxidative stress, hyperfiltration and glomerular hypertension are all contributing factors. Albuminuria, which is an early clinical manifestation of glomerular damage, is common in individuals with SCD. Kidney function declines more rapidly in individuals with SCD than in those with sickle cell trait or in healthy individuals. Multiple genetic modifiers, including APOL1, HMOX1, HBA1 and HBA2 variants are also implicated in the development and progression of SCD-related nephropathy. Chronic kidney disease and rapid decline in estimated glomerular filtration rate are associated with increased mortality in adults with SCD. Renin-angiotensin-aldosterone system inhibitors are the standard of care treatment for albuminuria in SCD, despite a lack of controlled studies demonstrating their long-term efficacy. Multiple studies of novel therapeutic agents are ongoing, and patients with SCD and kidney failure should be evaluated for kidney transplantation. Given the high prevalence and severe consequences of kidney disease, additional studies are needed to elucidate the pathophysiology, natural history and treatment of SCD-related nephropathy.

Extrarenal Effects of Aldosterone on Potassium Homeostasis

The role of aldosterone in regulating K⁺ excretion in the distal nephron is well established in kidney physiology. In addition to effects on the kidney, aldosterone modulates K⁺ and Na⁺ transport in salivary fluid, sweat, airway epithelia, and colonic fluid. More controversial and less well defined is the role of aldosterone in determining the internal distribution of K⁺ across cell membranes in nontransporting epithelia. In vivo studies have been limited by the difficulty in accurately measuring overall K⁺ balance and factoring in both variability and secondary changes in acid-base balance, systemic hemodynamics, and other K⁺-regulatory factors such as hormones and adrenergic activity. Despite these limitations, the aggregate data support a contributory role of aldosterone along with insulin and catecholamines in the normal physiologic regulation of internal K⁺ distribution. The authors speculate differences in tissue sensitivity to aldosterone may also contribute to differential tissue response of cardiac and skeletal muscle to conditions of total body K⁺ depletion.

Aldosterone-Regulated Sodium Transport and Blood Pressure

Aldosterone is a major mineralocorticoid steroid hormone secreted by glomerulosa cells in the adrenal cortex. It regulates a variety of physiological responses including those to oxidative stress, inflammation, fluid disruption, and abnormal blood pressure through its actions on various tissues including the kidney, heart, and the central nervous system. Aldosterone synthesis is primarily regulated by angiotensin II, K⁺ concentration, and adrenocorticotrophic hormone. Elevated serum aldosterone levels increase blood pressure largely by increasing Na⁺ re-absorption in the kidney through regulating transcription and activity of the epithelial sodium channel (ENaC). This review focuses on the signaling pathways involved in aldosterone synthesis and its effects on Na⁺ reabsorption through ENaC.

Heparin-Induced Renal Tubular Acidosis Masquerading as Hyperkalemia in a SARS-CoV-2 (COVID-19) Patient: A Case Report

Type 4 renal tubular acidosis (RTA) is a type of metabolic acidosis characterized by hyperchloremia and hyperkalemia resulting from the reduction in and/or resistance to aldosterone. RTA can be caused by multiple different medications including angiotensin-converting enzyme (ACE) inhibitor/angiotensin receptor blocker (ARB), potassium-sparing diuretics, and heparin. In this case, we discuss renal tubular acidosis caused by heparin use for the prevention of thromboembolic disease in COVID-19 infections.

Addison's disease associated with hypokalemia: a case report

BACKGROUND

Primary adrenal insufficiency (Addison's disease) is a rare medical condition usually associated with hyperkalemia or normokalemia. We report a rare case of Addison's disease, coexisting with hypokalemia, requiring treatment.

CASE PRESENTATION

In this case, a 42-year-old man was admitted to the intensive care unit with a history of loss of consciousness and severe hypoglycemia. His blood tests showed metabolic acidosis, low concentrations of cortisol 6 nmol/L (normal 68-327 nmol/L), and high plasma adrenocorticotropic hormone 253 pmol/L (normal 1.6-13.9 pmol/L), and he was diagnosed with primary adrenal insufficiency. Surprisingly, his serum potassium was low, 2.3 mmol/L (normal 3.5-5.1 mmol/L), requiring replacement over the course of his admission. Computed tomography scan of the adrenal glands showed features suggestive of unilateral adrenal tuberculosis. Investigations confirmed renal tubulopathy. The patient responded favorably to cortisol replacement, but never required fludrocortisone.

CONCLUSIONS

Coexistence of hypokalemia with Addison's disease is unusual. We recommend investigation of the cause of hypokalemia in its own right, if it occurs with primary adrenal insufficiency.

Mineralocorticoid Dysfunction during Critical Illness: A Review of the Evidence

The recent demonstration of the significant reduction in mortality in patients with septic shock treated with adjunctive glucocorticoids combined with fludrocortisone and the effectiveness of angiotensin II in treating vasodilatory shock have renewed interest in the role of the mineralocorticoid axis in critical illness. Glucocorticoids have variable interactions at the mineralocorticoid receptor. Similarly, mineralocorticoid receptor-aldosterone interactions differ from mineralocorticoid receptor-glucocorticoid interactions and predicate receptor-ligand interactions that differ with respect to cellular effects. Hyperreninemic hypoaldosteronism or selective hypoaldosteronism, an impaired adrenal response to increasing renin levels, occurs in a subgroup of hemodynamically unstable critically ill patients. The suggestion is that there is a defect at the level of the adrenal zona glomerulosa associated with a high mortality rate that may represent an adaptive response aimed at increasing cortisol levels. Furthermore, cross-talk exists between angiotensin II and aldosterone, which needs to be considered when employing therapeutic strategies.

Hyperkalemia: pathophysiology, risk factors and consequences

There have been significant recent advances in our understanding of the mechanisms that maintain potassium homoeostasis and the clinical consequences of hyperkalemia. In this article we discuss these advances within a concise review of the pathophysiology, risk factors and consequences of hyperkalemia. We highlight aspects that are of particular relevance for clinical practice. Hyperkalemia occurs when renal potassium excretion is limited by reductions in glomerular filtration rate, tubular flow, distal sodium delivery or the expression of aldosterone-sensitive ion transporters in the distal nephron. Accordingly, the major risk factors for hyperkalemia are renal failure, diabetes mellitus, adrenal disease and the use of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers or potassium-sparing diuretics. Hyperkalemia is associated with an increased risk of death, and this is only in part explicable by hyperkalemia-induced cardiac arrhythmia. In addition to its well-established effects on cardiac excitability, hyperkalemia could also contribute to peripheral neuropathy and cause renal tubular acidosis. Hyperkalemia-or the fear of hyperkalemia-contributes to the underprescription of potentially beneficial medications, particularly in heart failure. The newer potassium binders could play a role in attempts to minimize reduced prescribing of renin-angiotensin inhibitors and mineraolocorticoid antagonists in this context.

Hyponatremia and Hyporeninemic-Hypoaldosteronism in a Pediatric Intensive Care Unit Patient

Hyponatremia is one of the most commonly encountered electrolyte abnormalities encountered in the pediatric world. Defined as a serum or plasma sodium less than 135 mEq/L, the etiology of hyponatremia is one that can typically be determined by performance of a thorough history. However, occasionally the etiology of a patient's hyponatremia is more elusive and determined only after laboratory evaluation. We present a 6-year-old girl with a complex medical history including spinal muscular atrophy, tracheostomy and ventilator dependence, who was admitted to the pediatric intensive care unit for treatment and evaluation of seizures with hyponatremia that was initially thought to be due to syndrome of inappropriate anti-diuretic hormone or cerebral salt wasting. However, during her hospital course, it was determined that the hyponatremia was more indicative of a rarer and much less common cause of hyponatremia, hyporeninemic-hypoaldosteronism. The physiological factors controlling serum sodium are reviewed, the etiologies of hyponatremia are presented and the treatment of hyporeninemic-hypoaldosteronism is discussed.

Adrenal insufficiency: Physiology, clinical presentation and diagnostic challenges

Adrenal insufficiency (AI) is a serious condition, which can arise from pathology affecting the adrenal gland itself (primary adrenal insufficiency, PAI), hypothalamic or pituitary pathology (secondary adrenal insufficiency, SAI), or as a result of suppression of the hypothalamic-pituitaryadrenal (HPA) axis by exogenous glucocorticoid therapy (tertiary adrenal insufficiency, TAI). AI is associated with an increase in morbidity and mortality and a reduction in quality of life. In addition, the most common cause of PAI, autoimmune adrenalitis, may be associated with a variety of other autoimmune disorders. Untreated AI can present with chronic fatigue, weight loss and vulnerability to infection. The inability to cope with acute illness or infection can precipitate life-threatening adrenal crisis. It is therefore a critical diagnosis to make in a timely fashion, in order to institute appropriate management, aimed at reversing chronic ill health, preventing acute crises, and restoring quality of life. In this review, we will describe the normal physiology of the HPA axis and explain how knowledge of the physiology of this axis helps us understand the clinical presentation of AI, and forms the basis for the biochemical investigations which lead to the diagnosis of AI.

Identification of the fungicide epoxiconazole by virtual screening and biological assessment as inhibitor of human 11β-hydroxylase and aldosterone synthase

Humans are constantly exposed to a multitude of environmental chemicals that may disturb endocrine functions. It is crucial to identify such chemicals and uncover their mode-of-action to avoid adverse health effects. 11β-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) catalyze the formation of cortisol and aldosterone, respectively, in the adrenal cortex. Disruption of their synthesis by exogenous chemicals can contribute to cardio-metabolic diseases, chronic kidney disease, osteoporosis, and immune-related disorders. This study applied in silico screening and in vitro evaluation for the discovery of xenobiotics inhibiting CYP11B1 and CYP11B2. Several databases comprising environmentally relevant pollutants, chemicals in body care products, food additives and drugs were virtually screened using CYP11B1 and CYP11B2 pharmacophore models. A first round of biological testing used hamster cells overexpressing human CYP11B1 or CYP11B2 to analyze 25 selected virtual hits. Three compounds inhibited CYP11B1 and CYP11B2 with IC50 values below 3 μM. The most potent inhibitor was epoxiconazole (IC50 value of 623 nM for CYP11B1 and 113 nM for CYP11B2, respectively); flurprimidol and ancymidol were moderate inhibitors. In a second round, these three compounds were tested in human adrenal H295R cells endogenously expressing CYP11B1 and CYP11B2, confirming the potent inhibition by epoxiconazole and the more moderate effects by flurprimidol and ancymidol. Thus, the in silico screening, prioritization of chemicals for initial biological tests and use of H295R cells to provide initial mechanistic information is a promising strategy to identify potential endocrine disruptors inhibiting corticosteroid synthesis. A critical assessment of human exposure levels and in vivo evaluation of potential corticosteroid disrupting effects by epoxiconazole is required.

Epidemiology of hyperkalemia in chronic kidney disease

BACKGROUND

Hyperkalaemia is a significant electrolyte imbalance in chronic kidney disease (CKD). Renin-angiotensin-aldosterone system inhibitors (RAASi) have beneficial cardio-renal properties, although they can often cause hyperkalaemia.

OBJECTIVE

To examine the prevalence of hyperkalaemia in CKD, identify factors associated with its appearance and the relationship between hyperkalaemia and mortality.

PATIENTS AND METHODS

Retrospective observational study on patients with CKD in the period 1971-2017. The population was categorised into 3groups: Group 1, patients with CKD without renal replacement therapy; Group 2, patients on haemodialysis; and Group 3, patients on continuous ambulatory peritoneal dialysis.

RESULTS

A total of 2,629 patients were evaluated. The prevalence observed in the different groups was: 9.6%, 16.4% and 10.6%, respectively. Risk factors related to the appearance of hyperkalaemia in the CKD group were glomerular filtration rate (GFR) (P<.001), plasma creatinine (P<.001), plasma sodium (P<.001), haemoglobin (P=.028), diastolic blood pressure (P=.012), intake of ACE inhibitors and/or angiotensin ii receptor blockers (P=.008), treatment with metformin (P<.001) and diabetes (P=.045). Treatment with RAASi significantly increased hyperkalaemia as GFR decreased, as well as in patients with diabetes or heart failure.

CONCLUSIONS

Hyperkalaemia is a frequent metabolic alteration in CKD patients that increases in the presence of drugs with beneficial cardio-renal properties (RAASi), which means that patients often lose the benefit associated with these drugs. New, recently-appearing non-absorbable compounds, which bind to potassium in the gastrointestinal tract, enhancing faecal excretion and thus maintaining the cardio-renal benefit of the RAASi, could be relevant in the progress of patients with CKD.

Chronic Hyperkalemia in Cardiorenal Patients: Risk Factors, Diagnosis, and New Treatment Options

Chronic hyperkalemia (HK) is a serious medical condition that often manifests in patients with chronic kidney disease (CKD) and heart failure (HF) leading to poor outcomes and necessitating careful management by cardionephrologists. CKD, HF, diabetes, and renin-angiotensin-aldosterone system inhibitors use is known to induce HK. Current therapeutic options are not optimal, as pointed out by a large number of CKD and HF patients with HK. The following review will focus on the main risk factors for developing HK and also aims to provide a guide for a correct diagnosis and present new approaches to therapy.

Chronic hyperkalemia in non-dialysis CKD: controversial issues in nephrology practice

Chronic hyperkalemia is a major complication of chronic kidney disease (CKD) that occurs frequently, heralds poor prognosis, and necessitates careful management by the nephrologist. Current strategies aimed at prevention and treatment of hyperkalemia are still suboptimal, as evidenced by the relatively high prevalence of hyperkalemia in patients under stable nephrology care, and even in the ideal setting of randomized trials where best treatment and monitoring are mandatory. The aim of this review was to identify and discuss a range of unresolved issues related to the management of chronic hyperkalemia in non-dialysis CKD. The following topics of clinical interest were addressed: diagnosis, relationship with main comorbidities of CKD, therapy with inhibitors of the renin-angiotensin-aldosterone system, efficacy of current dietary and pharmacological treatment, and the potential role of the new generation of potassium binders. Opinion-based answers are provided for each of these controversial issues.

Dialysate potassium concentration: Should mass balance trump electrophysiology?

Nephrologists are faced with a difficult dilemma in choosing the ideal dialysis prescription to maintain neutral potassium mass balance. Should potassium mass balance goals prioritize the normalization of serum potassium levels using low potassium dialysate at the expense of provoking intradialytic arrhythmias, or should mass balance goals favor permissive hyperkalemia using higher dialysate potassium to avoid rapid intradialytic fluxes at the risk of more interdialytic arrhythmias? This review examines the factors that determine potassium mass balance among HD patients, the relationships between serum and dialysate potassium levels and outcomes, and concludes by examining currently available approaches to reducing risk of arrhythmias while managing potassium mass balance.

Hyporeninemic hypoaldosteronism in a patient with diabetes mellitus: an unforgettable case report

A 58-year-old man presented with a 3-year history of chronic and intermittent hyperkalemia requiring recurrent attendances to the emergency department for urgent treatment. His medical history included secondary diabetes mellitus following a bout of acute pancreatitis and a previous splenectomy for a spontaneous splenic rupture. He also had a history of prolonged use of non-steroidal anti-inflammatory drugs for back pain and painful neuropathy. He was not on any medication or diet that would cause a raised serum potassium level and his renal function was normal. He was on a basal-bolus insulin regimen but his diabetes control had been poor for several years. As the hyperkalemia had gone on for so long in the presence of normal renal function, he went on to have further tests. Adrenal insufficiency had been ruled out following a short Synacthen test. Further investigations revealed low serum aldosterone levels and inappropriately low serum renin levels in the presence of hyperkalemia. This was suggestive of hyporeninemic hypoaldosteronism (HH). He was then treated with fludrocortisone and furosemide and his serum potassium levels remained normal. Additionally, he did not require any more emergency admissions to treat hyperkalemia thereafter. It was concluded that the HH-induced hyperkalemia was caused by diabetes mellitus or due to a combination of diabetes and prolonged use of non-steroidal anti-inflammatory drugs. The absence of renal impairment may have contributed to the delay in diagnosis. HH is a commonly overlooked cause of hyperkalemia. This case highlights the fact that it should always be suspected when unexplained hyperkalemia is found in patients with only mild-moderately impaired renal function, especially in the presence of diabetes mellitus.

Type 2 diabetes mellitus and heart failure: a position statement from the Heart Failure Association of the European Society of Cardiology

The coexistence of type 2 diabetes mellitus (T2DM) and heart failure (HF), either with reduced (HFrEF) or preserved ejection fraction (HFpEF), is frequent (30-40% of patients) and associated with a higher risk of HF hospitalization, all-cause and cardiovascular (CV) mortality. The most important causes of HF in T2DM are coronary artery disease, arterial hypertension and a direct detrimental effect of T2DM on the myocardium. T2DM is often unrecognized in HF patients, and vice versa, which emphasizes the importance of an active search for both disorders in the clinical practice. There are no specific limitations to HF treatment in T2DM. Subanalyses of trials addressing HF treatment in the general population have shown that all HF therapies are similarly effective regardless of T2DM. Concerning T2DM treatment in HF patients, most guidelines currently recommend metformin as the first-line choice. Sulphonylureas and insulin have been the traditional second- and third-line therapies although their safety in HF is equivocal. Neither glucagon-like preptide-1 (GLP-1) receptor agonists, nor dipeptidyl peptidase-4 (DPP4) inhibitors reduce the risk for HF hospitalization. Indeed, a DPP4 inhibitor, saxagliptin, has been associated with a higher risk of HF hospitalization. Thiazolidinediones (pioglitazone and rosiglitazone) are contraindicated in patients with (or at risk of) HF. In recent trials, sodium-glucose co-transporter-2 (SGLT2) inhibitors, empagliflozin and canagliflozin, have both shown a significant reduction in HF hospitalization in patients with established CV disease or at risk of CV disease. Several ongoing trials should provide an insight into the effectiveness of SGLT2 inhibitors in patients with HFrEF and HFpEF in the absence of T2DM.

How Dangerous Is Hyperkalemia?

Hyperkalemia is a potentially life-threatening electrolyte disorder appreciated with greater frequency in patients with renal disease, heart failure, and with use of certain medications such as renin angiotensin aldosterone inhibitors. The traditional views that hyperkalemia can be reliably diagnosed by electrocardiogram and that particular levels of hyperkalemia confer cardiotoxic risk have been challenged by several reports of patients with atypic presentations. Epidemiologic data demonstrate strong associations of morbidity and mortality in patients with hyperkalemia but these associations appear disconnected in certain patient populations and in differing clinical presentations. Physiologic adaptation, structural cardiac disease, medication use, and degree of concurrent illness might predispose certain patients presenting with hyperkalemia to a lower or higher threshold for toxicity. These factors are often overlooked; yet data suggest that the clinical context in which hyperkalemia develops is at least as important as the degree of hyperkalemia is in determining patient outcome. This review summarizes the clinical data linking hyperkalemia with poor outcomes and discusses how the efficacy of certain treatments might depend on the clinical presentation.

Fludrocortisone therapy for persistent hyperkalaemia

BACKGROUND

Type 4 renal tubular acidosis causes hyperkalaemia, for which diabetes and medications commonly used in this patient group are aetiological factors. Here we describe the novel use of fludrocortisone in this difficult condition.

CASE REPORT

A 55-year-old woman with complex co-morbidities, including Type 2 diabetes (HbA_1c 37 mmol/mol 5.5%), was admitted with renal failure. Bloods on admission: eGFR 25 ml/min, creatinine 184 ?mol/L, urea 35.9 mmol/L, sodium 128 mmol/L, potassium 5.6 mmol/L, bicarbonate 15 mmol/L, and albumin 30 g/L. Her admission was prolonged, complicated by hospital-acquired sepsis (lower respiratory tract, urinary tract, and infected leg ulcers), poor venous access and severe depression. She had recurrent hyperkalaemia and deteriorating renal function, from presumed Type 4 renal tubular acidosis and excessive fluid losses from leg ulcers. Her renal function recurrently deteriorated, despite conventional treatment methods. After 69 days, she was commenced on fludrocortisone 50 mcg/day. Her renal function and serum potassium stabilized and she was discharged with potassium 4.3 mmol/L, eGFR 42 ml/min, and bicarbonate 23 mmol/L. She has remained stable on this treatment, without requiring further hospital admission for over 6 months, with eGFR 40 ml/min, and potassium 5.5 mmol/L, and albumin 26 g/L.

CONCLUSION

This woman was presumed to have Type 4 renal tubular acidosis and recurrent hyperkalaemia due to renal insufficiency, in the context of underlying diabetes and chronic kidney disease, which was poorly responsive to conventional management. There is limited evidence for using fludrocortisone in this setting. Our case suggests that fludrocortisone might offer a novel therapeutic strategy when conventional management is not working.

Hyponatremia in an Elderly Patient due to Isolated Hypoaldosteronism Occurring after Licorice Withdrawal

Hyponatremia is one of the most common electrolyte disorders encountered in the elderly. We present the case of an 81-year-old man who developed hyponatremia due to isolated hypoaldosteronism occurring after licorice withdrawal. He had severe hypokalemia with hypertension and was diagnosed with pseudoaldosteronism. He had been taking a very small dose of licorice as a mouth refresher since his early adulthood. Five months after licorice withdrawal, he developed hypovolemic hyponatremia, which was resolved with administration of fludrocortisone acetate. Our experience with this case suggests that isolated hypoaldosteronism occurring after licorice withdrawal should be considered as a potential cause of hyponatremia in elderly patients.

Challenges in the acute management of profound hyponatremia presenting with severe symptoms

Currently available guidelines in the acute management of severely symptomatic hypotonic hyponatremia vary in their approach to the use of hypertonic saline. In the acute setting, deciding on when to implement available treatment algorithm using hypertonic saline may be difficult, given that the duration of hyponatremia and potential alternative diagnoses presenting with similar symptoms may be hard to establish promptly. We present the case of a young female with symptomatic profound hyponatremia who subsequently developed osmotic demyelination syndrome due to rapid overcorrection of serum sodium concentration. We discuss the interplay between the dynamic pathophysiological processes responsible for hypotonic hyponatremia in adrenal insufficiency and conduct a detailed analysis of currently available guidelines to highlight the challenges in acute and reactive treatment in clinical practice.

Risk Factors for Developing Metabolic Acidosis after Radical Cystectomy and Ileal Neobladder

Purpose

To investigate the serial changes of metabolic acidosis and identify associated risk factors in patients who underwent radical cystectomy and ileal neobladder.

Material and Methods

From January 2010 to August 2014, 123 patients who underwent radical cystectomy and ileal neobladder reconstruction for bladder cancer were included in this study. Metabolic acidosis was defined as a serum bicarbonate level less than 22 mEq/L and impaired renal function was defined as a GFR <50ml/min. The presence of metabolic acidosis was evaluated at 1 month, 1 year, and 2 years after surgery. Multivariate logistic regression analysis was conducted to identify risk factors associated with development of metabolic acidosis.

Results

Metabolic acidosis was observed in 52%, 19.5%, and 7.3% of patients at 1 month, 1 year, and 2 years after surgery, respectively. At 1 month after surgery, impaired renal function was the only independent risk factor associated with metabolic acidosis (OR 3.87, P = 0.046). At 1 year after surgery, diabetes was the only independent risk factor associated with metabolic acidosis (OR 5.68, P = 0.002). At 2 years post-surgery, both age and diabetes were significant risk factors associated with metabolic acidosis.

Conclusion

Approximately, half of patients experienced metabolic acidosis one month after ileal neobladder reconstruction. Preoperative impaired renal function was the most significant risk factor for developing metabolic acidosis in the early postoperative period. However, the incidence of metabolic acidosis decreased to less than 20% 1 year after surgery, and diabetes was an independent risk factor during this period.

Changes in urinary potassium excretion in patients with chronic kidney disease

BACKGROUND

Hyperkalemia is one of the more serious complications of chronic kidney disease (CKD), and the cause of potassium retention is a reduction in urinary potassium excretion. However, few studies have examined the extent of the decrease of urinary potassium excretion in detail with respect to decreased renal function.

METHODS

Nine hundred eighty-nine patients with CKD (CKD stages G1 and G2 combined: 135; G3a: 107; G3b: 170; G4: 289; and G5: 288) were evaluated retrospectively. Values for urinary potassium excretion were compared between CKD stages, and the associations between urinary potassium excretion and clinical parameters, including diabetes mellitus status and use of renin-angiotensin-aldosterone system inhibitors, were analyzed using a multivariable linear regression analysis.

RESULTS

Urinary potassium excretion gradually decreased with worsening of CKD (G5: 24.8 ± 0.8 mEq/d, P < 0.001 vs. earlier CKD stages). In contrast, the value of fractional excretion of potassium at CKD G5 was significantly higher than that at the other stages (30.63 ± 0.93%, P < 0.001). Multivariable linear regression analysis revealed that urinary potassium excretion was independently associated with urinary sodium excretion (standardized coefficient, 0.499), the estimated glomerular filtration rate (0.281), and serum chloride concentration (-0.086).

CONCLUSION

This study demonstrated that urinary potassium excretion decreased with reductions in renal function. Furthermore, urinary potassium excretion was mainly affected by urinary sodium excretion and estimated glomerular filtration rate in patients with CKD, whereas the presence of diabetes mellitus and use of renin-angiotensin-aldosterone system inhibitors were not associated with urinary potassium excretion in this study.

Current and future treatment options for managing hyperkalemia

Hyperkalemia is associated with life-threatening cardiac arrhythmias and increased mortality. Hyperkalemia is most often observed in patients with chronic kidney disease and/or in those with congestive heart failure being treated with drugs that limit renal potassium excretion, especially drugs that inhibit the renin-angiotensin-aldosterone system. Treatment of hyperkalemia may be either acute, as needed during rapid changes in serum potassium, which are associated with cardiac arrhythmia, or chronic, which stabilizes serum potassium levels and limits the development of life-threatening arrhythmias. There are a number of both acute and chronic treatments available for the treatment of hyperkalemia, but some are limited by complex administration requirements and/or serious side effects. Hyperkalemia remains a vexing problem for clinicians, particularly in the care of patients with chronic kidney disease and cardiovascular disease.

Unique chloride-sensing properties of WNK4 permit the distal nephron to modulate potassium homeostasis

Dietary potassium deficiency activates thiazide-sensitive sodium chloride cotransport along the distal nephron. This may explain, in part, the hypertension and cardiovascular mortality observed in individuals who consume a low-potassium diet. Recent data suggest that plasma potassium affects the distal nephron directly by influencing intracellular chloride, an inhibitor of the with-no-lysine kinase (WNK)-Ste20p-related proline- and alanine-rich kinase (SPAK) pathway. As previous studies used extreme dietary manipulations, we sought to determine whether the relationship between potassium and NaCl cotransporter (NCC) is physiologically relevant and clarify the mechanisms involved. We report that modest changes in both dietary and plasma potassium affect NCC in vivo. Kinase assay studies showed that chloride inhibits WNK4 kinase activity at lower concentrations than it inhibits activity of WNK1 or WNK3. Also, chloride inhibited WNK4 within the range of distal cell chloride concentration. Mutation of a previously identified WNK chloride-binding motif converted WNK4 effects on SPAK from inhibitory to stimulatory in mammalian cells. Disruption of this motif in WNKs 1, 3, and 4 had different effects on NCC, consistent with the three WNKs having different chloride sensitivities. Thus, potassium effects on NCC are graded within the physiological range, which explains how unique chloride-sensing properties of WNK4 enable it to mediate effects of potassium on NCC in vivo.

Management of Hyperkalemia: An Update for the Internist

Hyperkalemia is a clinically important electrolyte abnormality that occurs most commonly in patients with chronic kidney disease. Due to its propensity to induce electrophysiological disturbances, severe hyperkalemia is considered a medical emergency. The management of acute and chronic hyperkalemia can be achieved through the implementation of various interventions, one of which is the elimination of medications that can raise serum potassium levels. Because many such medications (especially inhibitors of the renin-angiotensin aldosterone system) have shown beneficial effects in patients with cardiovascular and renal disease, their discontinuation for reasons of hyperkalemia represent an undesirable clinical compromise. The emergence of 2 new potassium-binding medications for acute and chronic therapy of hyperkalemia may soon allow the continued use of medications such as renin-angiotensin-aldosterone system inhibitors even in patients who are prone to hyperkalemia. This review article provides an overview of the physiology and the pathophysiology of potassium metabolism and hyperkalemia, the epidemiology of hyperkalemia, and its acute and chronic management. We discuss in detail emerging data about new potassium-lowering therapies, and their potential future role in clinical practice.

Advances in treatment of hyperkalemia in chronic kidney disease

INTRODUCTION

Hyperkalemia is a frequent electrolyte disorder associated with life-threatening cardiac arrhythmias and sudden death. Patients prone to hyperkalemia have chronic kidney disease (CKD) either alone or in conjunction with diabetes or heart failure (HF). Although agents inhibiting the renin-angiotensin-aldosterone-system (RAAS) are currently the first-line treatments toward cardio- and nephroprotection, their administration often leads to potassium elevation in such patients and results in high rates of treatment discontinuation.

AREAS COVERED

This article provides an overview of factors interfering with potassium homeostasis and discusses emerging potassium-lowering therapies for long-term management of hyperkalemia.

EXPERT OPINION

In recent randomized clinical studies, two new oral potassium-exchanging compounds, patiromer and sodium zirconium cyclosilicate, were shown to effectively normalize elevated serum potassium and chronically maintain potassium homeostasis in hyperkalemic patients treated with RAAS blockers. Both agents exhibit good tolerability and were not associated with serious adverse effects. Although additional research is required, these drugs are promising for lowering the risk of incident hyperkalemia associated with RAAS blockade use in people with diabetes or HF who have CKD. They also provide the opportunity to test whether patients who could not previously receive RAAS blockade may benefit from their cardio- and renoprotective effects.

A relationship between serum potassium concentration and insulin resistance in patients with type 2 diabetes mellitus

PURPOSE

In patients with type 2 diabetes mellitus (DM), insulin-stimulated glucose uptake is impaired. However, the relationship between serum potassium concentration and insulin resistance is poorly defined. This study aimed to investigate the association between serum potassium concentration and insulin resistance in these patients.

METHODS

Between April 2009 and October 2012, 180 patients with type 2 DM were analyzed. Insulin resistance was estimated using the homeostasis model and assessment (HOMA) index; resistance was defined as an index value of >2. The association between serum potassium concentration and insulin resistance was analyzed using linear regression methods. The incidence of hyperkalemia was also evaluated during follow-up.

RESULTS

Mean serum potassium concentration was 4.12 ± 0.47 mEq/l. The median HOMA index score was 2.1 (interquartile range 1.1-3.4). When the patients were compared based on insulin resistance, serum potassium concentration was higher in the patients with insulin resistance compared with the patients without (4.25 ± 0.48 vs. 4.09 ± 0.44 mEq/l, p = 0.015). The variables found to be the determinants of serum potassium concentration included female, renal function, serum sodium level, log aldosterone-to-plasma renin activity ratio, glycosylated hemoglobin, and log HOMA index. Over a mean follow-up period of 2.6 ± 1.1 years, 37 of 180 patients (21 %) experienced episodic hyperkalemia. Patients with insulin resistance experienced episodic hyperkalemia more frequently than those without.

CONCLUSIONS

Serum potassium concentration is likely to be increased in the patients with poorly controlled type 2 DM with insulin resistance than in those without insulin resistance.

Pathophysiology, diagnosis, and treatment of mineralocorticoid disorders

The renin-angiotensin-aldosterone system (RAAS) is a major regulator of blood pressure control, fluid, and electrolyte balance in humans. Chronic activation of mineralocorticoid production leads to dysregulation of the cardiovascular system and to hypertension. The key mineralocorticoid is aldosterone. Hyperaldosteronism causes sodium and fluid retention in the kidney. Combined with the actions of angiotensin II, chronic elevation in aldosterone leads to detrimental effects in the vasculature, heart, and brain. The adverse effects of excess aldosterone are heavily dependent on increased dietary salt intake as has been demonstrated in animal models and in humans. Hypertension develops due to complex genetic influences combined with environmental factors. In the last two decades, primary aldosteronism has been found to occur in 5% to 13% of subjects with hypertension. In addition, patients with hyperaldosteronism have more end organ manifestations such as left ventricular hypertrophy and have significant cardiovascular complications including higher rates of heart failure and atrial fibrillation compared to similarly matched patients with essential hypertension. The pathophysiology, diagnosis, and treatment of primary aldosteronism will be extensively reviewed. There are many pitfalls in the diagnosis and confirmation of the disorder that will be discussed. Other rare forms of hyper- and hypo-aldosteronism and unusual disorders of hypertension will also be reviewed in this article.

Plasma aldosterone and its relationship with left ventricular mass in hypertensive patients with early-stage chronic kidney disease

Plasma aldosterone concentrations (PACs) are often increased in the advanced stages of chronic kidney disease (CKD); however, PAC has not been fully investigated in early CKD. Moreover, little is known about the relationship between aldosteronemia and left ventricular (LV) mass in subjects with mild-to-moderate CKD. The study objectives were to analyze PAC, LV mass (LVM), LV geometry and their relationships, in a group of hypertensive patients with stage I-III CKD. One hundred ninety-five hypertensive patients with stage I-III CKD were enrolled and compared with a control group of 82 hypertensive patients without renal dysfunction. LVM was higher in subjects with CKD than in the control group and increased progressively with advancing stages of CKD (P=0.004). A similar trend was observed for PAC (P<0.0001), in which PAC was greater in CKD subjects with LV concentric geometry than in those with eccentric LV hypertrophy (P=0.01). Furthermore, in CKD patients, PAC was directly and significantly correlated with LVM (r=0.29; P<0.0001) and with relative wall thickness (RWT; r=0.36; P<0.0001). These associations remained significant even after adjustment for various confounding factors in multiple regression analyses (P<0.001). In summary, the results demonstrated that in CKD hypertensive patients, LVM, RWT and PAC are increased and related to each other from the earliest stages of renal dysfunction. Furthermore, it seems biologically plausible to speculate that aldosterone may promote a concentric geometry of the left ventricle and increase LVM in hypertensive patients with early CKD.

Renin knockout rat: control of adrenal aldosterone and corticosterone synthesis in vitro and adrenal gene expression

The classic renin-angiotensin system is partly responsible for controlling aldosterone secretion from the adrenal cortex via the peptide angiotensin II (ANG II). In addition, there is a local adrenocortical renin-angiotensin system that may be involved in the control of aldosterone synthesis in the zona glomerulosa (ZG). To characterize the long-term control of adrenal steroidogenesis, we utilized adrenal glands from renin knockout (KO) rats and compared steroidogenesis in vitro and steroidogenic enzyme expression to wild-type (WT) controls (Dahl S rat). Adrenal capsules (ZG; aldosterone production) and subcapsules [zona reticularis/fasciculata (ZFR); corticosterone production] were separately dispersed and studied in vitro. Plasma renin activity and ANG II concentrations were extremely low in the KO rats. Basal and cAMP-stimulated aldosterone production was significantly reduced in renin KO ZG cells, whereas corticosterone production was not different between WT and KO ZFR cells. As expected, adrenal renin mRNA expression was lower in the renin KO compared with the WT rat. Real-time PCR and immunohistochemical analysis showed a significant decrease in P450aldo (Cyp11b2) mRNA and protein expression in the ZG from the renin KO rat. The reduction in aldosterone synthesis in the ZG of the renin KO adrenal seems to be accounted for by a specific decrease in P450aldo and may be due to the absence of chronic stimulation of the ZG by circulating ANG II or to a reduction in locally released ANG II within the adrenal gland.

Heparin-induced hyperkalemia in a patient diagnosed with thyroid storm

OBJECTIVE

To describe a case of heparin-induced hyperkalemia and the role for transtubular potassium gradient (TTKG) to guide fludrocortisone therapy.

CASE SUMMARY

A 52-year-old white male developed hyperkalemia after receiving intravenous unfractionated heparin (UFH) for atrial fibrillation during thyroid storm. Admission laboratory results were noteworthy for normal potassium levels, undetectable thyroid-stimulating hormone, and mild transaminitis. Treatment for thyroid storm was initiated but UFH was stopped because the international normalized ratio was subsequently found to be elevated. Rising potassium levels developed just 24 hours after UFH discontinuation, without exogenous potassium supplementation, renal dysfunction, or acidosis. A TTKG was low, reflecting a hypoaldosterone state. In addition, the Naranjo probability scale indicated probable medication-associated hyperkalemia. Heparin-induced hyperkalemia (HIH) was suspected and oral fludrocortisone 0.2 mg was given daily alongside serial TTKG measurements. TTKG and hyperkalemia normalized with 2 days of treatment.

DISCUSSION

UFH is commonly used; therefore, clinicians must be cautious of hyperkalemia. Although HIH usually resolves after discontinuation of heparin, it may persist despite discontinuation of the drug, as highlighted by this case. In this setting, a TTKG should be determined, which can be used to guide fludrocortisone therapy.

CONCLUSIONS

HIH can occur despite discontinuation of heparin, and TTKG can be helpful in guiding fludrocortisone treatment in this circumstance.

Maternally-inherited diabetes with deafness (MIDD) and hyporeninemic hypoaldosteronism

Maternally-inherited diabetes with deafness (MIDD) is a rare form of monogenic diabetes that results, in most cases, from an A-to-G transition at position 3243 of mitochondrial DNA (m.3243A>G) in the mitochondrial-encoded tRNA leucine (UUA/G) gene. As the name suggests, this condition is characterized by maternally-inherited diabetes and bilateral neurosensory hearing impairment. A characteristic of mitochondrial cytopathies is the progressive multisystemic involvement with the development of more symptoms during the course of the disease. We report here the case of a patient with MIDD who developed hyporeninemic hypoaldosteronism.

[Tubular renal acidosis]

Renal tubular acidosis (RTAs) are a group of metabolic disorders characterized by metabolic acidosis with normal plasma anion gap. There are three main forms of RTA: a proximal RTA called type II and a distal RTA (type I and IV). The RTA type II is a consequence of the inability of the proximal tubule to reabsorb bicarbonate. The distal RTA is associated with the inability to excrete the daily acid load and may be associated with hyperkalaemia (type IV) or hypokalemia (type I). The most common etiology of RTA type IV is the hypoaldosteronism. The RTAs can be complicated by nephrocalcinosis and obstructive nephrolithiasis. Alkalinization is the cornerstone of treatment.

Potassium balances in maintenance hemodialysis

Potassium is abundant in the ICF compartment in the body and its excretion primarily depends on renal (about 90%), and to a lesser extent (about 10%) on colonic excretion. Total body potassium approximated to 50mmol/kg body weight and 2% of total body potassium is in the ECF compartment and 98% of it in the intracellular compartment.Dyskalemia is a frequent electrolyte imbalance observed among the maintenance hemodialysis patients. In case of hyperkalemia, it is frequently "a silent and a potential life threatening electrolyte imbalance" among patients with ESRD under maintenance hemodialysis. The prevalence of hyperkalemia in maintenance HD patients was reported to be about 8.7-10%. Mortality related to the hyperkalemia has been shown to be about 3.1/1,000 patient-years and about 24% of patients with HD required emergency hemodialysis due to severe hyperkalemia. In contrast to the hyperkalemia, much less attention has been paid to the hypokalemia in hemodialysis patients because of the low prevalence under maintenance hemodialysis patients. Severe hypokalemia in the hemodialysis patients usually was resulted from low potassium intake (malnutrition), chronic diarrhea, mineralocorticoid use, and imprudent use of K-exchange resins. Recently, the numbers of the new patients with advanced chronic kidney disease undergoing maintenance hemodialysis are tremendously increasing worldwide. However, the life expectancy of these patients is still much lower than that of the general population. The causes of excess mortality in these patients seem to various, but dyskalemia is a common cause among the patients with ESRD undergoing hemodialysis.