Although presently there are no reports that address the possible mechanisms underlying the relationship between SIADH and meningitis, we speculate that elevated levels of inflammatory cytokines such as IL-1 or IL-6, as observed in this disease, may lead to hyponatremia by augmenting ADH secretion. Riikonen et al.16)showed that high C-reactive protein (CRP) levels were associated with low serum sodium concentrations and that an elevation in CRP levels is an early indicator of bacteremia in neutropenic children. are found in inflammatory diseases, and their levels are higher in patients with hyponatremia. Because it is usually significantly correlated with the degree of inflammation in children, hyponatremia could be used as a diagnostic marker of pediatric inflammatory diseases. Based on available evidence, we hypothesize that hyponatremia may be associated with inflammatory diseases in general. Understanding the mechanisms responsible for augmented ADH secretion during inflammation, monitoring patient sodium levels, and selecting the appropriate intravenous fluid treatment are important components that may lower the morbidity and mortality of patients in a critical condition. Keywords:Hyponatremia, Inappropriate ADH Syndrome, Cytokines, Inflammatory disease, Crucial condition PD-1-IN-18 == Introduction == Hyponatremia, characterized by a serum sodium level that is less than 135 mEq/L, is one of the most commonly diagnosed electrolyte disorders in clinical medicine1). Although sodium deficiency prospects to hyponatremia, this condition is usually more commonly caused by solute dilution resulting from excessive consumption of water. Severe hyponatremia, where serum sodium level falls below <125 mEq/L, occurs in approximately 3% of all hospitalized patients2). Additionally, a rapid drop in serum sodium levels to 110-120 mEq/L prospects to cerebral edema and brain herniation1). Since it is usually often an indication of underlying disease, timely diagnosis of hyponatremia is usually of great importance in preventing potential morbidity and mortality3). Approximately one-third of all hyponatremic patients are diagnosed with euvolemic hyponatremia, a condition generally caused PD-1-IN-18 by the syndrome of improper antidiuretic hormone secretion (SIADH)4). Under normal physiological conditions, antidiuretic hormone (ADH; also known as vasopressin) is usually secreted from your posterior pituitary gland in Rabbit Polyclonal to OPN5 response to hyperosmolality in a process called osmotic ADH secretion. Osmotic ADH secretion prospects to lowering of serum osmolality. Nonosmotic ADH secretion, associated with hypovolemia, pain, nausea, and use of certain drugs, also prospects to hyponatremia5). Although nonosmotic ADH secretion can be a normal biological response when caused by PD-1-IN-18 hypovolemia or low effective arterial blood volume, it can also be a symptom of SIADH3). SIADH is usually characterized by euvolemia, high urinary sodium excretion (natriuresis), and elevated urine osmolality in the absence of diuretics. This syndrome is usually often associated with pituitary insufficiency, adrenal or renal dysfunctions, thyroid disorders, and edema3). ADH binds to the vasopressin-2 receptors in the renal collecting duct and stimulates a cyclic adenosine monophosphate-signaling cascade that leads to the insertion of preformed aquaporin-2 water channels into the apical plasma membrane, thereby resulting in the transcellular movement of water6). == Inflammation and hyponatremia: pathophysiological mechanisms == The development of hyponatremia is usually associated with numerous inflammatory diseases including pneumonia, severe acute respiratory distress syndrome, tuberculosis, meningitis, encephalitis, human immunodeficiency virus contamination, and malaria5). However, the pathophysiology of hyponatremia diagnosed under these inflammatory conditions remains elusive. Recent research revealed that inflammatory cytokines such as IL-1 and IL-6 are involved in the development of hyponatremia associated with inflammatory conditions, and that this process is related to ADH secretion5,7,8). Landgraf et al.9)reported that IL-1 stimulated both central and peripheral release of vasopressin in rats. In addition, Palin et al.10)reported that treatment of Wistar rats with lipopolysaccharide (LPS) resulted in reduced diuresis, elevated plasma arginine-vasopressin (AVP) levels, and an increase in the activity of AVP neurons. These authors also reported that a brain injection of IL-6 increased the activity of AVP neurons in a manner similar to that observed after peripheral LPS treatment. Accordingly, a brain injection of anti-IL-6 antibodies prevented the LPS-induced activation of AVP neurons. Therefore, these authors suggested that PD-1-IN-18 IL-6 PD-1-IN-18 induces an early activation of AVP neurons in response to a LPS injection10). Most notably, Mastorakos et al.11)exhibited that AVP levels were elevated 2 hours after IL-6 injection in all the six patients studied, suggesting that IL-6 activated the magno-cellular AVP-secreting neurons and that it may be involved in the development of an improper AVP secretion syndrome. Endothelial cells, easy muscle mass cells, and blood brain barrier (BBB) pericytes secrete IL-6 in response to IL-1 and LPS activation12,13). Circulating IL-6 can be transported across the BBB or may just diffuse across the BBB in the circumventricular organs5). Taken together, these findings suggest that inflammatory cytokines may regulate ADH secretion. == Inflammation and hyponatremia: clinical conditions == A number of studies have exhibited that hyponatremia is usually associated with numerous inflammatory conditions7,14-18). Very frequently, meningitis has been identified to be a cause of SIADH15). Patwari et al.15)reported that SIADH was diagnosed in 22 of 60 patients (36.7%) with bacterial meningitis on admission, and found that SIADH is significantly correlated with the severity of.