Antidiuretic hormone. Normal and disordered function

Effects of angiotensin-(1-7) on the proliferation and collagen synthesis of arginine vasopressin-stimulated rat cardiac fibroblasts: role of mas receptor-calcineurin-NF-κB signaling pathway

: Interstitial fibrosis is a common pathological change in various heart diseases, especially cardiac hypertrophy. Arginine vasopressin (AVP), one of the hallmarks of heart failure, exhibits a profibrotic effect by promoting the proliferation and differentiation of cardiac fibroblasts (CFs). In contrast, angiotensin-(1-7) [Ang-(1-7)] was reported to be beneficial for cardiac remodeling by its antifibrotic effect. To evaluate the effect of Ang-(1-7) on AVP-stimulated CFs and the subsequent signaling molecules involved, CFs isolated from neonatal rat hearts were incubated with AVP and treated with or without Ang-(1-7). Cell proliferation, cell cycle, collagen production, and related cellular signaling molecules were then assessed. The results showed that Ang-(1-7) dose-dependently inhibited cell proliferation and collagen production in AVP-stimulated CFs. In addition, Ang-(1-7) also significantly suppressed calcineurin activity in a dose-dependent manner in AVP-stimulated CFs, which was associated with reduced collagen production. Accordingly, the nuclear translocation and transcriptional activity of nuclear factor-kappa B (NF-κB), downstream signal of calcineurin, were also notably restrained by Ang-(1-7) in AVP-stimulated CFs. Furthermore, the inhibitory effect of Ang-(1-7) on AVP-activated calcineurin-NF-κB signaling was completely reversed by the Mas receptor antagonist A-799. These findings suggest that Ang-(1-7) exerts an antifibrotic effect by inhibiting AVP-stimulated CF proliferation and collagen synthesis by inactivating Mas receptor-calcineurin-NF-κB signaling pathway.

Copeptin: Limited Usefulness in Early Stroke Differentiation?

Background. Stroke can be a challenging diagnosis in an emergency-setting. We sought to determine whether copeptin may be a useful biomarker to differentiate between ischemic stroke (IS), transient ischemic attack (TIA), and stroke-mimics. Methods. In patients with suspected stroke arriving within 4.5 hours of symptom-onset, copeptin-levels were measured in initial blood-samples. The final diagnosis was adjudicated by vascular neurologists blinded to copeptin-values. Results. Of all 36 patients with available copeptin-values (median age 71 years, IQR: 54–76; 44% female), 20 patients (56%) were diagnosed with IS, no patient was diagnosed with hemorrhagic stroke, nine patients (25%) were diagnosed with TIA, and seven patients (19%) were stroke-mimics. Copeptin-levels (in pmol/L) tended to be higher in patients with IS [19.1 (11.2–48.5)] compared to TIA [9.4 (5.4–13.8)]. In stroke-mimics the range of values was extremely broad [33.3 (7.57–255.7)]. The diagnostic accuracy of copeptin for IS was 63% with a sensitivity of 80% and a positive predictive value of 64%. Conclusion. In this cohort of patients copeptin-levels within 4.5 hours of symptom onset were higher in patients with IS compared to TIA but the broad range of values in stroke-mimics limits diagnostic accuracy. This trial is registered with UTN: U1111-1119-7602.

Management of diabetes insipidus and adipsia in the child

Central diabetes insipidus (CDI) is a complex and heterogeneous clinical syndrome affecting the hypothalamic-neurohypophyseal network and water balance. A recent national surveillance in Denmark showed a prevalence rate of twenty-three CDI patients per 100,000 inhabitants in five years. The differential diagnosis between several presenting conditions with polyuria and polydipsia is puzzling, and the etiological diagnosis of CDI remains a challenge before the identification of an underlying cause. For clinical practice, a timely diagnosis for initiating specific treatment in order to avoid central nervous system damage, additional pituitary defects and the risk of dissemination of germ cell tumor is advisable. Proper etiological diagnosis can be achieved via a series of steps that start with careful clinical observation of several signs and endocrine symptoms and then progress to more sophisticated imaging tools. This review summarizes the best practice and approach for the diagnosis and treatment of patients with CDI.

Gender-specific co-activation of arginine vasopressin and the hypothalamic-pituitary-adrenal axis during stress

OBJECTIVE

To study the interaction between copeptin and hypothalamic-pituitary-adrenal (HPA) activation in men and women during hypoglycaemic stress.

DESIGN AND PATIENTS

A prospective study in 118 patients (mean age 47·7 ± 13·6 years, n = 52 women) undergoing insulin tolerance testing for suspected pituitary dysfunction.

MEASUREMENTS

Serum copeptin was measured in serially collected blood samples and assessed in relation to ACTH, cortisol and other endocrine parameters.

RESULTS

Symptomatic hypoglycaemia (mean glucose nadir, 1·6 ± 0·5 mmol/l) resulted in a rapid significant increase of serum copeptin. Individuals with impaired pituitary function had lower stress-induced copeptin levels (median, 6·26 pmol/l) than patients with intact pituitary (8·46 pmol/l, P < 0·001). A weak overall correlation between stress-induced copeptin and cortisol levels was observed (rs  = 0·31, P < 0·001). In female individuals, there was a positive correlation between stress-induced copeptin and ACTH (rs  = 0·47, P < 0·001) or cortisol levels (rs  = 0·42, P = 0·002), while in males, no correlation with ACTH levels (rs  = 0·03, P = 0·75) and poor correlation with cortisol levels (rs  = 0·24, P = 0·045) was observed. Patients with central diabetes insipidus showed lowest baseline (2·20 pmol/l) and stimulated copeptin levels (3·68 pmol/l).

CONCLUSIONS

The data from this study indicate that stress-induced release of AVP in women, but not in men, is linked to the co-activation of the hypothalamic-pituitary-adrenal system.

CT-pro-AVP as a tool for assessment of intravascular volume depletion in severe hyponatremia

BACKGROUND

Assessment of volume status is essential to best manage hyponatremic patients but is not always accurate in clinical practice. The aim of this study was to evaluate the reliability of C-terminal portion of pro-arginine-vasopressin (CT-pro-AVP), a surrogate biomarker of vasopressin release, in assessing intravascular volume (IVV) depletion in hypoosmolar hyponatremic patients.

METHODS

Plasma CT-pro-AVP and urea-to-creatinine ratio (Ur/Cr) were performed in 131 hospitalized patients presenting chronic severe hypoosmolar hyponatremia. At hospital discharge, their IVV was evaluated regardless of CT-pro-AVP concentrations. All patients were then classified as decreased or as normal/expanded IVV group.

RESULTS

Plasma CT-pro-AVP levels were higher in patients with decreased IVV (34.6 vs. 11.3 pmol/L, p<0.001) and exhibited a reliable performance for assessment of decreased IVV (ROC AUC at 0.717 [95% CI 0.629-0.805]). The combination of CT-pro-AVP and Ur/Cr resulted in an improved ROC AUC up to 0.787 (95% CI 0.709-0.866).

CONCLUSIONS

Our findings support the hypothesis that CT-pro-AVP plasma level may reflect IVV and would be a tool for its assessment. This performance has been magnified by its combination with Ur/Cr. A dual-marker strategy may help clinicians to optimize the management of severe hyponatremia especially in case of confusing clinical presentations.

Inappropriate arginine vasopressin levels and hyponatremia associated with cyclic vomiting syndrome

We herein describe two children who presented with attacks of severe cyclic vomiting. The primary case was a 2.5-year-old girl with a history of several admissions with vomiting and altered mental status. She was diagnosed with cyclic vomiting syndrome (CVS). During her attacks she developed significant hyponatremia on several occasions, which prompted us to measure plasma arginine vasopressin (AVP) levels during attacks. We found inappropriately high AVP levels with concomitant hyponatremia. We also measured plasma AVP and plasma sodium in another child with CVS who did not develop manifest hyponatremia but showed inappropriately elevated plasma AVP levels. Since the standard treatment of CVS consists of fluids, high plasma AVP levels may lead to dilutional hyponatremia. We would therefore like to emphasize the importance of close assessment of electrolyte levels in patients with CVS to avoid water intoxication.

Diagnostic performance of copeptin in patients with acute nontraumatic chest pain: BWH-TIMI ED chest pain study

BACKGROUND

Arginine-vasopressin (AVP) is an acute marker of physiologic stress. Copeptin is the C-terminal fragment of vasopressin precursor hormone that is more easily measured than AVP. Studies assessing the utility of copeptin in the diagnosis of myocardial infarction (MI) have demonstrated mixed results.

HYPOTHESIS

The aim of this study was to test the hypothesis that copeptin improves diagnostic performance when added to troponin for detecting MI in patients presenting to the emergency department with nontraumatic chest pain.

METHODS

We measured copeptin, local cardiac troponin I (local cTnI), and a contemporary sensitive cardiac troponin I (sensitive cTnI) at presentation and serially in patients who presented with acute chest pain. A copeptin cutoff of 14 pmol/L was utilized.

RESULTS

MI was diagnosed in 25.7% of patients. Noncoronary acute cardiopulmonary causes of chest pain occurred in 12.8%. Patients with MI had significantly higher copeptin levels than patients with noncardiac chest pain (P < 0.001). The area under the receiver operating characteristic curve (AUC) for copeptin was 0.60 (95% confidence interval: 0.54-0.66), significantly less than the AUC for local cTnI (0.92) or sensitive cTnI (0.96). The combination of copeptin with either the local or sensitive troponin assay (c-statistics 0.92 and 0.95, respectively) did not significantly improve the AUC as compared to either troponin assay alone. This finding persisted in the subgroup of early presenters (≤ 6 hours from symptom onset).

CONCLUSIONS

Copeptin did not improve the diagnostic performance for detecting MI when used alone or in combination with a contemporary sensitive cTnI assay, though our cohort had relatively few early presenters.

Plasma oxytocin and vasopressin do not predict neuropeptide concentrations in human cerebrospinal fluid

The involvement of the neuropeptides oxytocin (OXT) and vasopressin (AVP) in human socio-emotional behaviours is attracting increasing attention. There is ample evidence for elevated plasma levels upon a wide variety of social and emotional stimuli and scenarios, ranging from romantic love via marital distress up to psychopathology, with cause versus consequence being largely unclear. The present study examined whether plasma levels of both OXT and AVP are reflective of central neuropeptide levels, as assumed to impact upon socio-emotional behaviours. Concomitant plasma and cerebrospinal fluid (CSF) samples were taken from 41 non-neurological and nonpsychiatric patients under basal conditions. Although OXT and AVP levels in the CSF exceeded those in plasma, there was no correlation between both compartments, clearly suggesting that plasma OXT and AVP do not predict central neuropeptide concentrations. Thus, the validity of plasma OXT and AVP as potential biomarkers of human behaviour needs further clarification.

The evolutionary origin of the vasopressin/V2-type receptor/aquaporin axis and the urine-concentrating mechanism

In this mini-review, current evidence for how the vasopressin/V2-type receptor/aquaporin axis developed co-evolutionary as a crucial part of the urine-concentrating mechanism will be presented. The present-day human kidney, allowing the concentration of urine up to a maximal osmolality around 1200 mosmol kg(-1)-or urine to plasma osmolality ratio around 4-with essentially no sodium secreted is the result of up to 3 billion years evolution. Moving from aquatic to terrestrial habitats required profound changes in kidney morphology, most notable the loops of Henle modifying the kidneys from basically a water excretory system to a water conserving system. Vasopressin-like molecules has during the evolution played a significant role in body fluid homeostasis, more specifically, the osmolality of body liquids by controlling the elimination/reabsorption of fluid trough stimulating V2-type receptors to mobilize aquaporin water channels in the renal collector tubules. Recent evidence supports that all components of the vasopressin/V2-type receptor/aquaporin axis can be traced back to early precursors in evolutionary history. The potential clinical and pharmacological implications of a better phylogenetic understanding of these biological systems so essential for body fluid homeostasis relates to any pathological aspects of the urine-concentrating mechanism, in particular deficiencies of any part of the vasopressin-V2R-AQP2 axis causing central or nephrogenic diabetes insipidus-and for broader patient populations also in preventing and treating disturbances in human circadian regulation of urine volume and osmolality that may lead to enuresis and nocturia.

Atmospheric conditions, lunar phases, and childbirth: a multivariate analysis

Our objective was to assess extrinsic influences upon childbirth. In a cohort of 1,826 days containing 17,417 childbirths among them 13,252 spontaneous labor admissions, we studied the influence of environment upon the high incidence of labor (defined by 75th percentile or higher), analyzed by logistic regression. The predictors of high labor admission included increases in outdoor temperature (odds ratio: 1.742, P = 0.045, 95%CI: 1.011 to 3.001), and decreases in atmospheric pressure (odds ratio: 1.269, P = 0.029, 95%CI: 1.055 to 1.483). In contrast, increases in tidal range were associated with a lower probability of high admission (odds ratio: 0.762, P = 0.030, 95%CI: 0.515 to 0.999). Lunar phase was not a predictor of high labor admission (P = 0.339). Using multivariate analysis, increases in temperature and decreases in atmospheric pressure predicted high labor admission, and increases of tidal range, as a measurement of the lunar gravitational force, predicted a lower probability of high admission.

Unexpected fatal hypernatremia after successful cardiopulmonary resuscitation with therapeutic hypothermia: a case report

Central diabetes insipidus (DI), characterized by unexpected fatal hypernatremia, is a rare complication after successful cardiopulmonary resuscitation with therapeutic hypothermia, but may be potentially fatal if recognition is delayed. We describe here a patient who experienced cardiac arrest due to a pulmonary embolism, followed by successful resuscitation after induction of therapeutic hypothermia. The patient, however, suddenly developed unexpected hypernatremia with increased urine output and was diagnosed with central DI as a complication of cerebral edema, and eventually died. Our findings suggest that central DI should be considered as a possible complication following unexpected hypernatremia with increased urine output during therapeutic hypothermia and that desmopressin acetate should be used to treat central DI.

Effect of loading dose and formulation on safety and efficacy of conivaptan in treatment of euvolemic and hypervolemic hyponatremia

PURPOSE

The effect of loading dose and formulation on the safety and efficacy of conivaptan in the treatment of euvolemic and hypervolemic hyponatremia was studied.

METHODS

This parallel-group study randomized 121 hospitalized patients with euvolemic or hypervolemic hyponatremia to one of four treatment regimens: placebo loading dose followed by conivaptan continuous i.v. infusion using the ampul formulation (regimen 1), conivaptan loading dose followed by continuous i.v. infusion using the ampul formulation (regimen 2), placebo loading dose followed by conivaptan continuous i.v. infusion using the premixed formulation (regimen 3), or conivaptan loading dose followed by continuous i.v. infusion using the premixed formulation (regimen 4). The primary variable was the incidence and severity of injection-site reactions (ISRs), as evaluated using the ISR modified 5-point scale (ISRMS). Secondary outcomes included effects on serum sodium concentration (SSC), duration of effect, and safety and tolerability.

RESULTS

All four dosing regimens were efficacious, safe, and well tolerated. No significant differences in ISRMS scores or differences in changes from baseline SSC or in the duration of effects on SSC were observed between the regimens. Overly rapid SSC increases occurred in 7%, 7%, 3%, and 21% of patients treated with regimens 1, 2, 3, and 4, respectively. Overall, adverse events related to general disorders and ISRs occurred in 39%, 43%, 53%, and 55% of patients receiving regimens 1, 2, 3, and 4, respectively.

CONCLUSION

Intravenous conivaptan regimens with or without a loading dose, whether using the ampul or a premixed formulation, had similar safety, tolerability, and efficacy in patients with euvolemic or hypervolemic hyponatremia. The pre-mixed formulation used with a loading dose may be associated with an increased frequency of overly rapid increase in SSC compared with the other regimens studied.

Central diabetes insipidus associated with impaired renal aquaporin-1 expression in mice lacking liver X receptor β

The present study demonstrates a key role for the oxysterol receptor liver X receptor β (LXRβ) in the etiology of diabetes insipidus (DI). Given free access to water, LXRβ(-/-) but not LXRα(-/-) mice exhibited polyuria (abnormal daily excretion of highly diluted urine) and polydipsia (increased water intake), both features of diabetes insipidus. LXRβ(-/-) mice responded to 24-h dehydration with a decreased urine volume and increased urine osmolality. To determine whether the DI was of central or nephrogenic origin, we examined the responsiveness of the kidney to arginine vasopressin (AVP). An i.p. injection of AVP to LXRβ(-/-) mice revealed a partial kidney response: There was no effect on urine volume, but there was a significant increase of urine osmolality, suggesting that DI may be caused by a defect in central production of AVP. In the brain of WT mice LXRβ was expressed in the nuclei of magnocellular neurons in the supraoptic and paraventricular nuclei of the hypothalamus. In LXRβ(-/-) mice the expression of AVP was markedly decreased in the magnocellular neurons as well as in urine collected over a 24-h period. The persistent high urine volume after AVP administration was traced to a reduction in aquaporin-1 expression in the kidney of LXRβ(-/-) mice. The LXR agonist (GW3965) in WT mice elicited an increase in urine osmolality, suggesting that LXRβ is a key receptor in controlling water balance with targets in both the brain and kidney, and it could be a therapeutic target in disorders of water balance.

Copeptin is associated with one-year mortality and functional outcome in patients with acute spontaneous basal ganglia hemorrhage

High plasma copeptin levels have been found to be associated with short-term poor outcome after intracerebral hemorrhage (ICH). We furthermore evaluate the relation of plasma copeptin levels to long-term outcome and early neurological deterioration after ICH. Fifty healthy controls and 89 patients with acute spontaneous basal ganglia hemorrhage were recruited in this study. Plasma copeptin concentrations on admission measured by enzyme-linked immunosorbent assay were considerably high in patients than healthy controls. A multivariate analysis identified plasma copeptin level as an independent predictor for 1-year mortality, 1-year unfavorable outcome (modified Rankin Scale score>2) and early neurological deterioration. A receiver operating characteristic curve showed that the predictive value of plasma copeptin concentration was similar to that of National Institutes of Health Stroke Scale scores for long-term poor outcome and early neurological deterioration. However, copeptin did not obviously improve the predictive values of National Institutes of Health Stroke Scale scores. Thus, increased plasma copeptin level is an independent prognostic marker of 1-year mortality, 1-year unfavorable outcome and early neurological deterioration after ICH.

Hyponatraemia in imported malaria: the pathophysiological role of vasopressin

BACKGROUND

In the pathophysiology of hyponatraemia in malaria, the relative contribution of appropriate and inappropriate arginine vasopressin (AVP) release is unknown; the trigger for inappropriate AVP release is also unknown.

METHODS

Serum copeptin, a stable and sensitive marker for AVP release, was analysed in a large cohort of patients with imported malaria (204 patients) and in a small prospective substudy (23 patients) in which urine sodium and osmolality were also available. Hyponatraemia was classified as mild (serum sodium 131-134 mmol/l) and moderate-to-severe (< 131 mmol/l).

RESULTS

Serum copeptin on admission was higher in patients with moderate-to-severe hyponatraemia (median 18.5 pmol/L) compared with normonatraemic patients (12.7 pmol/L, p < 0.05). Despite prompt fluid resuscitation, the time to normalization of serum sodium was longer in patients with moderate-to-severe hyponatraemia (median 2.9 days) than in patients with mild hyponatraemia (median 1.7 days, p < 0.001). A poor correlation was found between serum sodium and copeptin levels on admission (rs = -0.17, p = 0.017). Stronger correlations were identified between serum C-reactive protein and copeptin (rs = -0.36, p < 0.0001) and between serum C-reactive protein and sodium (rs = 0.33, p < 0.0001). Data from the sub-study suggested inappropriate AVP release in seven of 13 hyponatraemic malaria patients; these patients had significantly higher body temperatures on admission.

CONCLUSIONS

In hyponatraemic patients with imported malaria, AVP release was uniformly increased and was either appropriate or inappropriate. Although the exact trigger for inappropriate AVP release remains unknown, the higher body temperatures, correlations with C-reactive protein and long normalization times of serum sodium, suggest an important role of the host inflammatory response to the invading malaria parasite.

High-sensitivity troponin T and copeptin in non-ST acute coronary syndromes: implications for prognosis and role of hsTnT and copeptin in non-STEACS

High-sensitivity TnT (hsTnT) has been proposed to improve the diagnosis and stratification in acute coronary syndromes. Copeptin has been proposed for a rapid and accurate rule out of acute myocardial infarction, but some doubts exist about its use out of the first hours from admission. Abnormalities of serum hsTnT and copeptin levels in non-STEACS and negative TnT, could have prognostic implications. Methods. We included 122 non-STEACS patients without raised TnT, 33 disease controls and 43 healthy controls. We measured hsTnT and copeptin levels. Clinical follow-up at 12 months was performed for adverse endpoints. Results. Non-STEACS patients had raised hsTnT compared with both control groups (P = 0.036 and P < 0.001). Copeptin levels were higher in non-STEACS patients than healthy controls (P = 0.021), without differences with disease controls. Raised levels of hs-TnT presented prognostic implications [HR 3.29 (95%CI: 1.33–7.49), P = 0.010]. hs-TnT could be used for invasive approach decision, as it shows prognostic relevance in conservative approach-patients whereas remains unrelevant for catheterized-patients. Copeptin levels were not associated with adverse events. Conclusion. hsTnT levels increased in non-STEACS, were predictive of adverse events and could be important for recommending an invasive management. We cannot confirm a predictive role of copeptin out of the first hours from admission.

Pediatric disorders of water balance

Fluid homeostasis requires adequate water intake, regulated by an intact thirst mechanism and appropriate free water excretion by the kidneys, mediated by appropriate secretion of arginine vasopressin (AVP, also known as antidiuretic hormone). AVP exerts its antidiuretic action by binding to the X chromosome-encoded V2 vasopressin receptor (V2R), a G protein coupled receptor on the basolateral membrane of renal collecting duct epithelial cells. After V2R activation, increased intracellular cyclic adenosine monophosphate mediates shuttling of the water channel aquaporin 2 to the apical membrane of collecting duct cells, resulting in increased water permeability and antidiuresis. Clinical disorders of water balance are common, and abnormalities in many steps involving AVP secretion and responsiveness have been described. This article focuses on the principal disorders of water balance, diabetes insipidus, and the syndrome of inappropriate antidiuretic hormone secretion.

Familial forms of diabetes insipidus: clinical and molecular characteristics

Over the past two decades, the genetic and molecular basis of familial forms of diabetes insipidus has been elucidated. Diabetes insipidus is a clinical syndrome characterized by the excretion of abnormally large volumes of diluted urine (polyuria) and increased fluid intake (polydipsia). The most common type of diabetes insipidus is caused by lack of the antidiuretic hormone arginine vasopressin (vasopressin), which is produced in the hypothalamus and secreted by the neurohypophysis. This type of diabetes insipidus is referred to here as neurohypophyseal diabetes insipidus. The syndrome can also result from resistance to the antidiuretic effects of vasopressin on the kidney, either at the level of the vasopressin 2 receptor or the aquaporin 2 water channel (which mediates the re-absorption of water from urine), and is referred to as renal or nephrogenic diabetes insipidus. Differentiation between these two types of diabetes insipidus and primary polydipsia can be difficult owing to the existence of partial as well as complete forms of vasopressin deficiency or resistance. Seven different familial forms of diabetes insipidus are known to exist. The clinical presentation, genetic basis and cellular mechanisms responsible for them vary considerably. This information has led to improved methods of differential diagnosis and could provide the basis of new forms of therapy.

Novel mutation in the AVPR2 gene in a Danish male with nephrogenic diabetes insipidus caused by ER retention and subsequent lysosomal degradation of the mutant receptor

Mutations in the arginine vasopressin receptor 2 (AVPR2) gene can cause X-linked nephrogenic diabetes insipidus (NDI) characterized by the production of large amounts of urine and an inability to concentrate urine in response to the antidiuretic hormone vasopressin. We have identified a novel mutation in the AVPR2 gene (L170P) located in the fourth transmembrane domain in a Danish NDI male. Analysis of the mutant receptor in Madin-Darby Canine Kidney cell culture revealed that AVPR2-L170P was retained in the endoplasmic reticulum, and the expression was dramatically downregulated compared to wild-type AVPR2. Inhibition of the lysosome resulted in increased intracellular accumulation of AVPR2-L170P, indicating that AVPR2-L170P is downregulated via the lysosome. Inhibition of the proteasome resulted in plasma membrane localization of AVPR2-L170P, although the overall levels of AVPR2-L170P were unchanged.

Correlation of plasma copeptin and vasopressin concentrations in hypo-, iso-, and hyperosmolar States

BACKGROUND

Copeptin, the C-terminal moiety of provasopressin, is cosecreted with vasopressin. Copeptin may be a useful parameter to characterize disorders of water homeostasis and can be readily measured in plasma or serum. However, it is unknown to date how circulating copeptin and vasopressin levels correlate at different plasma osmolalites.

OBJECTIVE

To correlate plasma copeptin with plasma osmolality and vasopressin concentrations in healthy subjects during iso-, hypo-, and hyperosmolar states.

METHODS

Plasma osmolalities, copeptin, and vasopressin levels were measured in 20 volunteers at baseline, after an oral water load, and during and after iv infusion of 3% saline. Correlation coefficients were determined between plasma osmolalites and copeptin and vasopressin concentrations, as well as between vasopressin and copeptin concentrations.

RESULTS

Median plasma osmolalities decreased from 290 mOsm/kg (range, 284-302) at baseline to 281 (273-288) mOsm/kg after water load and rose to 301 (298-307) mOsm/kg after hypertonic saline. Median plasma copeptin concentrations decreased from 3.3 (1.1-36.4) pm at baseline to 2.0 (0.9-10.4) pm after water load and increased to 13.6 (3.7-43.3) pm after hypertonic saline. Vasopressin and copeptin concentrations correlated with plasma osmolality (Spearman's rank correlation coefficient 0.49 and 0.77, respectively). There was a close correlation of vasopressin and copeptin concentrations (Spearman's rank correlation coefficient 0.8).

CONCLUSION

Plasma vasopressin and copeptin correlate strongly over a wide range of osmolalities in healthy individuals. Therefore, the measurement of copeptin, which remains stable for several days, is a useful alternative to vasopressin measurements and will likely facilitate the differential diagnosis of disorders of water metabolism.

[Current considerations in syndrome of inappropriate secretion of antidiuretic hormone/syndrome of inappropriate antidiuresis]

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH)/syndrome of inappropriate antidiuresis is characterized by a hypotonic hyponatremia, with an insufficiently diluted urine given the plasmatic hypoosmolality, in the absence of hypovolemia (with or without a third space), hypotension, renal or heart failure, cirrhosis of the liver, hypothyroidism, adrenal insufficiency, vomiting, or other non-osmotic stimuli of ADH secretion. The response of ADH to the infusion of hypertonic saline divides SIADH into 4 different types. In type D, there is no alteration in ADH secretion. Rather, the defect is the maintained permeability of kidney aquaporin-2 channels to water. Activating mutations of the V2 receptor have been identified. The most frequent cause of SIADH is the use of drugs that induce secretion of the hormone. Old age is per se a risk factor for its development. SIADH is underdiagnosed, and hospitalization often worsens the clinical situation, due to an iatrogenic excess in the use of oral and i.v. liquids, often hypotonic, together with a reduction in salt intake. Treatment is directed towards normalization of natremia when possible, together with the avoidance of both hyponatremic encephalopathy as well as the osmotic demyelinization syndrome. Cases of "appropriate" secretion of ADH with normovolemic hyponatremia and high mortality rates should be treated with the same urgency as SIADH--such is the case of post-surgical hyponatremia.

Hyponatremia in acute decompensated heart failure: mechanisms, prognosis, and treatment options

Hyponatremia is common and is increasingly recognized as an independent prognostic marker that adversely affects morbidity and mortality in various disease states, including heart failure. In acute decompensated heart failure (ADHF), the degree of hyponatremia often parallels the severity of cardiac dysfunction and is further exacerbated by any reduction in glomerular filtration rate and arginine vasopressin dysregulation. A recent study showed that even modest improvement of hyponatremia may have survival benefits. Although management of hyponatremia in ADHF has traditionally focused on improving cardiac function and fluid restriction, the magnitude of improvement of serum sodium is fairly slow and unpredictable. In this article, we discuss the mechanisms of hyponatremia in ADHF, review its evolving prognostic significance, and evaluate the efficacy of various treatments for hyponatremia, including the recently approved vasopressin receptor antagonists for managing hyponatremia among patients hospitalized for ADHF.

Vaptans for the treatment of hyponatremia

The vaptans constitute a new class of pharmaceuticals developed for the treatment of the hypervolemic and euvolemic forms of hyponatremia. These agents are nonpeptide vasopressin antagonists that interfere with the antidiuretic effect of the hormone by competitively binding to V(2) receptors in the kidney. This blockade results in water diuresis (aquaresis) that, if not offset by increased fluid intake, reduces body water content and raises plasma sodium levels. Probably as a result of this rise in plasma sodium, thirst and plasma vasopressin concentration increase, potentionally limiting the effects of the vasopressin antagonists. Nonetheless, vaptans are particularly useful to treat hypervolemic hyponatremia associated with severe congestive heart failure or chronic liver failure, as the only other treatments currently available, such as fluid restriction and diuretics, are slow-acting and minimally effective. Vaptans are also useful for treating euvolemic hyponatremia associated with the syndrome of inappropriate antidiuretic hormone (SIADH), at least when it is chronic and/or minimally symptomatic. However, because their effects vary unpredictably from patient to patient, vaptans are less useful than hypertonic saline infusion in cases of acute, severe and symptomatic hyponatremia. Vaptan therapy is absolutely contraindicated in hypovolemic hyponatremia (in which total body water is reduced) and is ineffective in the vasopressin-independent form of inappropriate antidiuresis caused by constitutive activating mutations of V(2) receptors.

The relationship between arginine vasopressin levels and hyponatremia following a percutaneous renal biopsy in children receiving hypotonic or isotonic intravenous fluids

Post-operative hyponatremia is a common complication in children which results from hypotonic fluid administration in the presence of arginine vasopressin (AVP) excess. We evaluated the relationship between the change in serum sodium and AVP levels following percutaneous renal biopsy in children receiving either hypotonic or isotonic fluids. This study was prompted after we encountered a patient who developed near-fatal hyponatremic encephalopathy following a renal biopsy while receiving hypotonic fluids. The relationship between the change in serum sodium and AVP levels was evaluated prior to (T0) and at 5 h (T5) following a percutaneous renal biopsy in 60 children receiving either hypotonic (0.6% NaCl, 90 mEq/L) or isotonic fluids (0.9% NaCl, 154 mEq/L). The proportion of patients with elevated AVP levels post-procedure was similar between those receiving 0.6 or 0.9% NaCl (30 vs. 26%). Patients receiving 0.6% NaCl with elevated AVP levels experienced a fall in serum sodium of 1.9 ± 1.5 mEq/L, whereas those receiving 0.9% NaCl had a rise in serum sodium of 0.85 ± 0.34 mEq/L with no patients developing hyponatremia. There were no significant changes in serum sodium levels in patients with normal AVP concentrations post-procedure in either group. In conclusion, elevated AVP levels were common among our patients following a percutaneous renal biopsy. Isotonic fluids prevented a fall in serum sodium and hyponatremia, while hypotonic fluids did not.

High plasma mid-regional pro-adrenomedullin levels in children with severe dengue virus infections

BACKGROUND

Dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) is characterized by hemorrhage, plasma leakage and shock. Adrenomedullin and vasopressin are vaso-active hormones that mediate endothelial permeability, vascular tone and water balance and may therefore play a role during DHF/DSS. Adrenomedullin reduces endothelial permeability and has vasodilatory properties, while vasopressin is a potent vasoconstrictor with anti-diuretic effects.

OBJECTIVES

To determine mid-regional pro-adrenomedullin (MR-proADM) and copeptin, which are reliable and stable markers for adrenomedullin and vasopressin response, respectively, and relate their plasma concentrations to outcome and markers of plasma leakage in Indonesian children with DHF and DSS.

STUDY DESIGN

In this observational cohort study Indonesian children with DHF/DSS were enrolled. On study days 0 and 2, plasma MR-proADM and copeptin concentrations as well as parameters of plasma leakage were determined. Plasma MR-proADM and copeptin concentrations were compared to values of healthy controls.

RESULTS

MR-proADM was increased in both DHF (n=43) and DSS (n=28) vs. controls (n=17), with median (IQR) values of 0.47 (0.40-0.68), 0.56 (0.44-1.00) vs. 0.22 (0.19-0.29) nmol/L, respectively. Additionally, MR-proADM correlated with signs of increased vascular leakage such as low albumin and increased pleural effusion. Copeptin concentrations showed no significant changes as compared to controls.

CONCLUSIONS

MR-proADM concentrations are elevated in children with DHF and DSS and correlate with the severity of plasma leakage, in contrast to copeptin concentrations. We speculate that adrenomedullin has a functional role in limiting endothelial hyperpermeability during DHF/DSS. Finally, MR-proADM may be a candidate biomarker to predict development of DHF/DSS.

Co-peptin: Role as a novel biomarker in clinical practice

BACKGROUND

Arginine vasopressin (AVP) is a key regulator of water balance, but its instability makes reliable measurement difficult and precludes its routine use. Co-peptin is the C-terminal part of the AVP precursor which plays an important role in the correct structural formation of the AVP precursor and its efficient proteolytic maturation. Because of its stoichiometric generation, co-peptin mirrors the release of AVP and measurement of more stable co-peptin may be an indicator of AVP levels.

METHOD

A comprehensive literature search was conducted from the websites of the National Library of Medicine (http://www.ncbl.nlm.nih.gov) and Pubmed Central, the US National Library of Medicine's digital archive of life sciences literature (http://www.pubmedcentral.nih.gov/). The data was assessed from books and journals that published relevant articles in this field.

RESULT

Recent and ongoing research indicates the diagnostic and prognostic roles of co-peptin in various clinical settings especially in critically ill patients.

CONCLUSION

Co-peptin levels are altered in various physiological and pathological conditions indicating its possible role as a biomarker. However, further research using co-peptin in various clinical settings will prove its cost-effectiveness and clinical usefulness.

Hyponatremia and brain injury: absence of alterations of serum brain natriuretic peptide and vasopressin

OBJECTIVE

To study any possible relation between hyponatremia following brain injury and the presence of cerebral salt-wasting syndrome (CSWS) or the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), and if vasopressin, brain natriuretic peptide (BNP) and aldosterone have a role in its mechanism.

METHOD

Patients with brain injury admitted to the intensive care unit were included and had their BNP, aldosterone and vasopressin levels dosed on day 7.

RESULTS

Twenty six adult patients were included in the study. Nine (34.6%) had hyponatremia and presented with a negative water balance and higher values of urinary sodium, serum potassium and diuresis than patients with normonatremia. The serum levels of BNP, aldosterone, and vasopressin were normal and no relation was observed between plasma sodium and BNP, aldosterone or vasopressin.

CONCLUSION

The most likely cause of hyponatremia was CSWS and there was no correlation between BNP, aldosterone and vasopressin with serum sodium level.

Increased mortality in hypernatremic burned patients

Introduction: In-hospital hypernatremia develops usually iatrogenically from inadequate or inappropriate fluid prescription. In severely burned patient an extensive initial fluid resuscitation is necessary for burn shock survival. After recovering of cellular integrity the circulating volume has to be normalized. Hereby extensive water and electrolyte shifts can provoke hypernatremia.

Purpose: Is a hypernatremic state associated with increased mortality?

Method: Retrospective study for the incidence of hypernatremia and survival in 40 patients with a totally burned surface area (TBSA) >10%. Age, sex, TBSA, ABSI-Score and fluid resuscitation within the first 24 hours were analyzed. Patients were separated in two groups without (Group A) or with (Group B) hypernatremia.

Results: Hypernatremia occurred on day 5±1.4. No significant difference for age, sex, TBSA, ABSI-Score and fluid resuscitation within the first 24 hours were calculated. In Group A all patients survived, while 3 of the hypernatremic patient in Group B died during ICU-stay (Odds-ratio = 1.25; 95% CI 0.971–1.61; p=0.046).

Conclusion: Burned patients with an in-hospital acquired hypernatremia have an increased mortality risk. In case of a hypernatremic state early intervention is obligatory. There is a need of a fluid removal strategy in severely burned patient to avoid water imbalance.

Copeptin is associated with mortality and outcome in patients with acute intracerebral hemorrhage

Background

Spontaneous intracerebral hemorrhage (ICH) accounts for a high mortality and morbidity. Early prediction of outcome is crucial for optimized care and treatment decision. Copeptin, the C-terminal part of provasopressin, has emerged as a new prognostic marker in a variety of diseases, but its prognostic value in ICH is unknown.

Methods

In 40 consecutive patients who were admitted to the hospital within 72 hours after a spontaneous ICH, the plasma copeptin level was measured with a sandwich immunoassay upon admission. The prognostic value of copeptin to predict 30 day mortality and functional outcome after 90 days was assessed. A favorable outcome was defined as a Barthel score above 85 and a score below 3 on the Modified Rankin Scale.

Results

Copeptin correlated positively with hematoma volume (r = 0.32, p < 0.05) and negatively with the Glasgow Coma Scale (GCS) on admission (r = -0.35, p < 0.05). Copeptin levels were higher in patients who died within 30 days than in 30-day survivors (179.0 pmol/l (IQR 33.7- 566.0) vs. 12.9 pmol/l (IQR 5.2 - 42.8), p = 0.003). Copeptin levels were also higher in patients with an unfavorable functional outcome at 90 days compared to patients with a favorable outcome (32.4 pmol/l (IQR 9.5-97.8) vs. 11.9 pmol/l (IQR 3.2-19.8), p = 0.04). For the prediction of death, receiver-operating-characteristics analysis revealed an area under the curve (AUC) for copeptin of 0.88 (95%CI 0.75-1.00). The predictive value of the copeptin concentration was thus similar to that of GCS (AUC 0.82 (95%CI 0.59-1.00) p = 0.53), of the ICH Score (AUC 0.89, (95%CI 0.76-1.00), p = 0.94) and the ICH Grading Scale (AUC 0.86 (95%CI 0.69-1.00), p = 0.81).

Conclusions

Copeptin is a new prognostic marker in patients with an ICH. If this finding can be confirmed in larger studies, copeptin might be an additional valuable tool for risk stratification and decision-making in the acute phase of ICH.

Trial Registration

(Clinical Trial Registration: ISCTRN00390962)

Tolvaptan: a new tool for the effective treatment of hyponatremia in psychotic disorders

IMPORTANCE OF THE FIELD

Hyponatremia (serum sodium concentration < 136 mEq/liter) is a common and potentially life-threatening medical comorbidity seen in patients with psychotic disorders. Tolvaptan, a selective antagonist of the V(2)-receptor, is FDA-approved for the treatment of clinically significant hypervolemic and euvolemic hyponatremia. This represents a major development in the care of psychotic individuals with hyponatremia.

AREAS COVERED IN THE REVIEW

This review provides an overview of the existing literature on prevalence rates and risk factors associated with hyponatremia in psychotic patients (1923 - present). Tolvaptan is discussed as a potential advance in the treatment of hyponatremia in patients with psychotic disorders, and preliminary data are reviewed.

WHAT THE READER WILL GAIN

The reader will gain an appreciation of the prevalence of hyponatremia among psychotic individuals, an understanding of the distinctions between acute and chronic hyponatremia in this population, and awareness that effective treatments are becoming available.

TAKE HOME MESSAGE

A modest literature exists regarding prevalence rates and risk factors associated with hyponatremia in psychotic populations. Hyponatremia is common and serious enough to merit clinical concern. Perhaps, now that tolvaptan has been FDA-approved, progress will accelerate and new insights will develop that begin to bring relief from this medical comorbidity among psychotic patients.

Conivaptan for the treatment of hyponatremia

Conivaptan is the first dual vasopressin V1a/V2 receptor antagonist approved by the US FDA for the treatment of euvolemic and hypervolemic hyponatremia in hospitalized patients. Short-term use of intravenous conivaptan has been shown to promote effective free-water duresis and resolution of hyponatremia in several clinical trials. Adverse effects reported with short-term use mostly include infusion site reactions. However, they may also include serious effects including unexpectedly rapid serum Na⁺ correction, hypokalemia and orthostatic hypotension. Despite its proven efficacy in hospitalized patients, the development of oral conivaptan has been discontinued due to its shared hepatic clearance with many commonly used drugs. Thus, data is lacking on the long-term efficacy of conivaptan in patients with chronic hyponatremia. The decision to use conivaptan in addition to conventional therapy for euvolemic or hypervolemic hyponatremic patients must be carefully considered according to the patient history and response to conventional treatment.

Biomarkers: a definite plus in pneumonia

During the past few years, biomarkers have emerged as an indispensible tool in the diagnosis of pneumonia. To find an ideal diagnostic biomarker for pneumonia is not an easy task. Not only should it allow an early diagnosis of the condition, but it should also allow differential diagnosis from other noninfectious conditions. Ongoing research is being done in this field so as to put an array of biomarkers at the disposal of doctors to improve the diagnosis of pneumonia when patients present to them with cough or nonspecific symptoms which could easily be misinterpreted as symptoms of other conditions. Procalcitonin and soluble triggering receptor expressed on myeloid cells-1 have emerged as reliable diagnostic markers in pneumonia, and are better when compared to other markers, namely, C-reactive protein, leukocyte count, and proinflammatory cytokines. Many other biomarkers are being studied for their probable use in diagnosing pneumonia but have yet to prove their benefit.

Prevention of hyponatremia during maintenance intravenous fluid administration: a prospective randomized study of fluid type versus fluid rate

OBJECTIVES

To determine the importance of sodium content versus administration rate of intravenous fluids in the development of hyponatremia in postoperative children.

STUDY DESIGN

In this prospective, randomized, nonblinded study, 124 children admitted for surgery received 0.9% (NS) or 0.45% (N/2) saline solution at 100% or 50% maintenance rates. Plasma electrolytes, osmolality, and ADH at induction of anesthesia were compared with values 8 hours (T(8)), and 24 hours (T(24); n = 67) after surgery. Blood glucose and ketones were measured every 4 hours. Electrolytes and osmolality were measured in urine samples.

RESULTS

Plasma sodium concentrations fell in both N/2 groups at T(8) (100%: -1.5 +/- 2.3 mmol/L 50%: -1.9 +/- 2.0 mmol/L; P < .01) with hyponatremia more common than in the NS groups at T(8) (30% vs 10%; P = .02) but not T(24). Median plasma antidiuretic hormone concentrations increased 2- to 4-fold during surgery (P < or = .001) and only reattained levels at induction of anesthesia by T(24) in the N/2 100% group. On multiple linear regression analysis, fluid type, not rate determined risk of hyponatremia (P < .04). Two children on 100% developed SIADH (1NS). Fourteen (23%; 7NS) on 50% maintenance were assessed as dehydrated. Dextrose content was increased in 18 for hypoglycemia or ketosis.

CONCLUSIONS

The risk of hyponatremia was decreased by isotonic saline solution but not fluid restriction.

Hyponatremia in patients with neurologic disorders

The kidney and the brain play a major role in maintaining normal homeostasis of the extracellular fluid by neuroendocrine regulation of sodium and water balance. Therefore, disturbances of sodium balance are common in patients with central nervous system (CNS) disorders and clinicians should focus not only on the CNS lesion, but also on the potentially deleterious complications. Hyponatremia is the most common and important electrolyte disorder affecting patients with critical neurologic diseases. In these patients, the maladaptation to hyponatremia by impaired osmoregulation in pathologic lesions of brain may cause more aggressive cerebral edema and increased intracranial pressure due to hypoosmolality induced by hyponatremia. Furthermore, hyponatremia accompanied by CNS disorders has shown to increase delayed cerebral ischemia and mortality rates. Two main pathophysiologies of hyponatremia, excluding iatrogenic causes, are inappropriate secretion of antidiuretic hormone (SIADH) and cerebral salt wasting (CSW) syndrome. Differential diagnosis between these two entities can be difficult due to considerable overlap in the laboratory findings and clinical situations. SIADH is in a volume expanded status due to inappropriately secreted arginine vasopressin (AVP) and requires water restriction. However, CSW syndrome is characterized by renal sodium wasting mainly due to increased natriuretic peptides resulting in volume depletion and follows appropriate secretion of AVP. Therefore, maintenance of volume status and sodium replacement is the mainstay of treatment in CSW syndrome. In this review, we aimed to describe the regulation of sodium and water balance, and pathophysiology, diagnosis and treatment of hyponatremia in neurologic patients, especially focusing on SIADH and CSW syndrome.

Pediatric disorders of water balance

Fluid homeostasis requires adequate water intake, regulated by an intact thirst mechanism and appropriate free water excretion by the kidneys, mediated by appropriate secretion of arginine vasopressin (AVP, also known as antidiuretic hormone). AVP exerts its antidiuretic action by binding to the X chromosome-encoded V2 vasopressin receptor (V2R), a G protein-coupled receptor on the basolateral membrane of renal collecting duct epithelial cells. After V2R activation, increased intracellular cyclic adenosine monophosphate mediates shuttling of the water channel aquaporin 2 to the apical membrane of collecting duct cells, resulting in increased water permeability and antidiuresis. Clinical disorders of water balance are common, and abnormalities in many steps involving AVP secretion and responsiveness have been described. This article focuses on the principal disorders of water balance, diabetes insipidus, and the syndrome of inappropriate antidiuretic hormone secretion.

Plasma levels of copeptin in patients with coronary heart disease

The present study was undertaken to investigate alteration in plasma levels of copeptin, a stable fragment derived from provasopressin, in patients with coronary heart disease. We measured plasma level of copeptin in 21 patients with coronary heart disease (CHD) and 12 age-matched healthy subjects by radioimmunoassay (RIA). Chi-square test, Student's t-test and one-way analysis of variance were used for statistical analyses. Correlations between variables were tested by simple linear regression analysis. The plasma level of copeptin was significantly increased in patients (43.07 +/- 17.08 vs 11.13 +/- 5.73 pmol/l in controls, P < 0.01) and was further increased, by 60%, to 68.71 +/- 16.81 pmol/l on day 1 after therapy with percutaneous transluminal coronary angioplasty (PTCA) and stent (P < 0.05). On days 3 and 7 after therapy, the levels were greatly decreased, to 38.82 +/- 19.00 and 32.10 +/- 14.00 pmol/l, respectively, from that before therapy (all P < 0.05) but were higher, by 249% and 188%, respectively, than that of controls (all P < 0.01). The results suggest that the vasopressin system is activated in patients with CHD as indicated by changes in copeptin level, especially after PTCA and stent therapy. As a potential risk factor for CHD, plasma copeptin activation might have important clinical significance in terms of early intervention in patients with CHD.

Agonist-independent interactions between beta-arrestins and mutant vasopressin type II receptors associated with nephrogenic syndrome of inappropriate antidiuresis

Nephrogenic syndrome of inappropriate antidiuresis is a recently identified genetic disease first described in two unrelated male infants with severe symptomatic hyponatremia. Despite undetectable arginine vasopressin levels, patients have inappropriately concentrated urine resulting in hyponatremia, hypoosmolality, and natriuresis. It was found that each infant had a different mutation of the vasopressin type II receptor (V2R) at codon 137 where arginine was converted to cysteine or leucine (R137C or R137L), resulting in constitutive signaling. Interestingly, a missense mutation at the same codon, converting arginine to histidine (R137H), leads to the opposite disease phenotype with a loss of the kidney's ability to concentrate urine resulting in nephrogenic diabetes insipidus. This mutation is associated with impaired signaling, although whether this is predominantly due to impaired trafficking to the plasma membrane, agonist-independent internalization, or G protein uncoupling is currently unclear. Using bioluminescence resonance energy transfer and confocal microscopy, we demonstrate that both V2R-R137C and V2R-R137L mutants interact with beta-arrestins in an agonist-independent manner resulting in dynamin-dependent internalization. This phenotype is similar to that observed for V2R-R137H, which is intriguing considering that it is accompanied by constitutive rather than impaired signaling. Consequently, it would seem that agonist-independent internalization per se is unlikely to be the major determinant of impaired V2R-R137H signaling. Our findings indicate that the V2R-R137C and V2R-R137L mutants traffic considerably more efficiently to the plasma membrane than V2R-R137H, identifying this as a potentially important mutation-dependent difference affecting V2R function.

Differentiating appropriate antidiuretic hormone secretion, inappropriate antidiuretic hormone secretion and cerebral salt wasting: the common, uncommon, and misnamed

PURPOSE OF REVIEW

Causes of hyponatremia in children include the syndrome of appropriate antidiuretic hormone secretion, the syndrome of inappropriate antidiuretic hormone secretion and cerebral salt wasting. The purpose of this review is to distinguish these possibilities, focusing on cerebral salt wasting.

RECENT FINDINGS

Most cases of hyponatremia in children are due to the syndrome of appropriate antidiuretic hormone secretion. The syndrome of inappropriate antidiuretic hormone secretion can be seen with neurological injury, pain and medication use. Recent studies suggest that cerebral salt wasting is a rare cause of hyponatremia. When cerebral salt wasting is diagnosed, it is often difficult to make a direct link with the central nervous system insult.

SUMMARY

The clinical condition, assessment of extracellular fluid space volume status, measurement of urinary electrolytes and responses to infusion of saline solutions can distinguish between syndrome of appropriate antidiuretic hormone secretion, syndrome of inappropriate antidiuretic hormone secretion and cerebral salt wasting. The word 'cerebral' in 'cerebral salt wasting syndrome' can thus be inappropriate, conveying inaccurate causation.