No abstract

The direct measurement of hypertonic saline-stimulated plasma copeptin had greater diagnostic accuracy than the water-deprivation test in patients with hypotonic polyuria. (Funded by the Swiss National Foundation and others; ClinicalTrials.gov number, NCT01940614 .).

No abstract

Diagnosis and management of diabetes insipidus for the internist: an update (Review).

Clinical Endocrinology. 2019;91:22-32. wileyonlinelibrary.com/journal/cen 1 | INTRODUC TI ON Arginine vasopressin (AVP) is the main regulating hormone of body fluid homeostasis. It is secreted from the posterior pituitary upon osmotic or nonosmotic stimuli, with the main osmotic stimulus being increased plasma osmolality and the main nonosmotic stimulus being hypovolaemia and promotes water reabsorption via V2 receptors in the kidney, thereby normalizing hypertonicity and vasomotor tone. Disorders of body fluid homeostasis are common and can be divided into hyper-and hypoosmolar circumstances: the classical AbstractCopeptin is secreted in an equimolar amount to arginine vasopressin (AVP) but can easily be measured in plasma or serum with a sandwich immunoassay. The main stimuli for copeptin are similar to AVP, that is an increase in osmolality and a decrease in arterial blood volume and pressure. A high correlation between copeptin and AVP has been shown. Accordingly, copeptin mirrors the amount of AVP in the circulation.Copeptin has, therefore, been evaluated as diagnostic biomarker in vasopressin-dependent disorders of body fluid homeostasis. Disorders of body fluid homeostasis are common and can be divided into hyper-and hypoosmolar circumstances: the classical hyperosmolar disorder is diabetes insipidus, while the most common hypoosmolar disorder is the syndrome of inappropriate antidiuresis (SIAD). Copeptin measurement has led to a "revival" of the direct test in the differential diagnosis of diabetes insipidus. Baseline copeptin levels, without prior thirsting, unequivocally identify patients with nephrogenic diabetes insipidus. In contrast, for the difficult differentiation between central diabetes insipidus and primary polydipsia, a stimulated copeptin level of 4.9 pmol/L upon hypertonic saline infusion differentiates these two entities with a high diagnostic accuracy and is clearly superior to the classical water deprivation test. On the contrary, in the SIAD, copeptin measurement is of only little diagnostic value. Copeptin levels widely overlap in patients with hyponatraemia and emphasize the heterogeneity of the disease. Additionally, a variety of factors lead to unspecific copeptin elevations in the acute setting further complicating its interpretation. The broad use of copeptin as diagnostic marker in hyponatraemia and specifically to detect cancer-related disease in SIADH patients can, therefore, not be recommended. K E Y W O R D Scopeptin, diabetes insipidus, diagnosis, hypernatremia, hyponatraemia, primary polydipsia, SIAD This is an open access article under the terms of the Creat ive Commo ns Attri bution-NonCo mmerc ial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

BackgroundTreatment options to address the hyponatremia induced by the syndrome of inappropriate antidiuresis (SIAD) are inadequate. The sodium glucose cotransporter 2 (SGLT2) inhibitor empagliflozin promotes osmotic diuresis via urinary glucose excretion and therefore, might offer a novel treatment option for SIAD.MethodsIn this double-blind, randomized trial, we recruited 88 hospitalized patients with SIAD-induced hyponatremia <130 mmol/L at the University Hospital Basel from September 2016 until January 2019 and assigned patients to receive, in addition to standard fluid restriction of <1000 ml/24 h, a once-daily dose of oral empagliflozin or placebo for 4 days. The primary end point was the absolute change in plasma sodium concentration after 4 days of treatment. Secondary end points included predisposing factors for treatment response and safety of the intervention.ResultsOf the 87 patients who completed the trial, 43 (49%) received treatment with empagliflozin, and 44 (51%) received placebo. Baseline plasma sodium concentrations were similar for the two groups (median 125.5 mmol/L for the empaflozin group and median 126 mmol/L for the placebo group). Patients treated with empagliflozin had a significantly higher increase of median plasma sodium concentration compared with those receiving placebo (10 versus 7 mmol/L, respectively; P=0.04). Profound hyponatremia (<125 mmol/L) and lower baseline osmolality levels increased the likelihood of response to treatment with empagliflozin. Treatment was well tolerated, and no events of hypoglycemia or hypotension occurred among those receiving empagliflozin.ConclusionsAmong hospitalized patients with SIAD treated with fluid restriction, those who received empagliflozin had a larger increase in plasma sodium levels compared with those who received placebo. This finding indicates that empagliflozin warrants further study as a treatment for the disorder.

No abstract

BackgroundHypernatraemia is common in inpatients and is associated with substantial morbidity. Its differential diagnosis is challenging, and delayed treatment may have devastating consequences. The most important hormone for the regulation of water homeostasis is arginine vasopressin, and copeptin, the C-terminal portion of the precursor peptide of arginine vasopressin, might be a reliable new parameter with which to assess the underlying cause of hypernatraemia.MethodsIn this prospective, multicentre, observational study conducted in two tertiary referral centres in Switzerland, 92 patients with severe hyperosmolar hypernatraemia (Na+ > 155 mmol/L) were included. After a standardised diagnostic evaluation, the underlying cause of hypernatraemia was identified and copeptin levels were measured.ResultsThe most common aetiology of hypernatraemia was dehydration (DH) (n = 65 [71%]), followed by salt overload (SO) (n = 20 [22%]), central diabetes insipidus (CDI) (n = 5 [5%]) and nephrogenic diabetes insipidus (NDI) (n = 2 [2%]). Low urine osmolality was indicative for patients with CDI and NDI (P < 0.01). Patients with CDI had lower copeptin levels than patients with DH or SO (both P < 0.01) or those with NDI. Copeptin identified CDI with an AUC of 0.99 (95% CI 0.97–1.00), and a cut-off value ≤ 4.4pmol/L showed a sensitivity of 100% and a specificity of 99% to predict CDI. Similarly, urea values were lower in CDI than in DH or SO (P < 0.05 and P < 0.01, respectively) or NDI. The AUC for diagnosing CDI was 0.98 (95% CI 0.96–1.00), and a cut-off value < 5.05 mmol/L showed high specificity and sensitivity for the diagnosis of CDI (98% and 100%, respectively). Copeptin and urea could not differentiate hypernatraemia induced by DH from that induced by SO (P = 0.66 and P = 0.30, respectively).ConclusionsCopeptin and urea reliably identify patients with CDI and are therefore helpful tools for therapeutic management in patients with severe hypernatraemia.Trials registrationClinicalTrials.gov, NCT01456533. Registered on 20 October 2011.Electronic supplementary materialThe online version of this article (10.1186/s13054-018-1955-7) contains supplementary material, which is available to authorized users.