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Simple Summary: This review article is focused on hyponatremia in cancer patients. Hyponatremia is the most common electrolyte disorder in these patients and there is evidence that it negatively affects the course of the disease. Basic research has shown an increased proliferation rate and motility of cells cultured in low [Na+] conditions. Interestingly, the vasopressin receptor antagonist tolvaptan, originally approved for the treatment of hyponatremia secondary to the syndrome of inappropriate antidiuresis, and subsequently in polycystic kidney disease, counteracts cancer cell proliferation and invasivity in vitro. This result might encourage the design of clinical trials to determine whether tolvaptan may also have a role against cancer on clinical grounds. Hyponatremia is the most common electrolyte disorder encountered in hospitalized patients. This applies also to cancer patients. Multiple causes can lead to hyponatremia, but most frequently this electrolyte disorder is due to the syndrome of inappropriate antidiuresis. In cancer patients, this syndrome is mostly secondary to ectopic secretion of arginine vasopressin by tumoral cells. In addition, several chemotherapeutic drugs induce the release of arginine vasopressin by the hypothalamus. There is evidence that hyponatremia is associated to a more negative outcome in several pathologies, including cancer. Many studies have demonstrated that in different cancer types, both progression-free survival and overall survival are negatively affected by hyponatremia, whereas the correction of serum [Na+] has a positive effect on patient outcome. In vitro studies have shown that cells grown in low [Na+] have a greater proliferation rate and motility, due to a dysregulation in intracellular signalling pathways. Noteworthy, vasopressin receptors antagonists, which were approved more than a decade ago for the treatment of euvolemic and hypervolemic hyponatremia, have shown unexpected antiproliferative effects. Because of this property, vaptans were also approved for the treatment of polycystic kidney disease. In vitro evidence indicated that this family of drugs effectively counteracts proliferation and invasivity of cancer cells, thus possibly opening a new scenario among the pharmacological strategies to treat cancer. [ABSTRACT FROM AUTHOR]

Summary: Objective: To perform a meta‐analysis based on published studies that compared falls and bone fractures between patients with and without hyponatremia. Context: There is evidence suggesting that hyponatremia is associated with an increased risk of falls and bone fractures. Design: An extensive Medline, Embase and Cochrane search was performed to retrieve all studies published up to, 30 April 2017, using the following words: “hyponatremia” or “hyponatraemia” AND “falls” and “bone fractures.” A meta‐analysis was performed including all studies comparing falls and bone fractures in subjects with or without hyponatremia. Patients and Results: Of 216 retrieved articles, 15 studies satisfied inclusion criteria encompassing a total of 51 879 patients, of whom 2329 were hyponatremic. Across all studies, hyponatremia was associated with a significantly increased risk of falls (MH‐OR = 2.14[1.71; 2.67]. This result was confirmed when only hospitalized patients were considered (MH‐OR = 2.44 [1.97; 3.02]). A meta‐regression analysis showed that the hyponatremia‐related risk of falls was higher in those studies considering a lower serum [Na+] cut‐off to define hyponatremia. Interestingly, the estimated risk of falls related to hyponatremia was already significantly higher when a serum [Na+] cut‐off of 135 mmol/L was considered (MH‐OR = 1.26[1.23;1.29]). The presence of hyponatremia was also associated with a higher risk of fractures, particularly hip fractures (MH‐OR = 2.00[1.43;2.81]). Conclusions: This study confirms that hyponatremia is associated with an increased risk of falls and bone fractures. The clinical, social and economic relevance of such association is strengthened by the increased incidence of hyponatremia in older people. [ABSTRACT FROM AUTHOR]

Background: Hyponatremia is the most common electrolyte disorder in clinical practice, and evidence to date indicates that severe hyponatremia is associated with increased morbidity and mortality. The aim of our study was to perform a meta-analysis that included the published studies that compared mortality rates in subjects with or without hyponatremia of any degree. Methods and Findings: An extensive Medline, Embase and Cochrane search was performed to retrieve the studies published up to October 1st 2012, using the following words: “hyponatremia” and “mortality”. Eighty-one studies satisfied inclusion criteria encompassing a total of 850222 patients, of whom 17.4% were hyponatremic. The identification of relevant abstracts, the selection of studies and the subsequent data extraction were performed independently by two of the authors, and conflicts resolved by a third investigator. Across all 81 studies, hyponatremia was significantly associated with an increased risk of overall mortality (RR = 2.60[2.31–2.93]). Hyponatremia was also associated with an increased risk of mortality in patients with myocardial infarction (RR = 2.83[2.23–3.58]), heart failure (RR = 2.47[2.09–2.92]), cirrhosis (RR = 3.34[1.91–5.83]), pulmonary infections (RR = 2.49[1.44–4.30]), mixed diseases (RR = 2.59[1.97–3.40]), and in hospitalized patients (RR = 2.48[2.09–2.95]). A mean difference of serum [Na+] of 4.8 mmol/L was found in subjects who died compared to survivors (130.1±5.6 vs 134.9±5.1 mmol/L). A meta-regression analysis showed that the hyponatremia-related risk of overall mortality was inversely correlated with serum [Na+]. This association was confirmed in a multiple regression model after adjusting for age, gender, and diabetes mellitus as an associated morbidity. Conclusions: This meta-analysis shows for the first time that even a moderate serum [Na+] decrease is associated with an increased risk of mortality in commonly observed clinical conditions across large numbers of patients. [ABSTRACT FROM AUTHOR]