endocrine and metabolic disorders
Syndrome of Inappropriate ADH Secretion (SIADH)
Etiology of SIADH
Vasopressinrelease can be enhanced by a number of central nervous system disorders. In addition, ectopicvasopressinmay be produced by certain cancers or pulmonary disorders (see table). In some patients,vasopressinrelease is appropriately suppressed but at a lower-than-normal plasma osmolality (reset osmostat). Many medications cause fluid retention which can result in dilutional hyponatremia. Some medications triggervasopressinrelease and/or potentiate the renal effect of endogenousvasopressin; some have a directvasopressin-like effect on the kidneys (eg,oxytocin,desmopressin). There is some debate as to whether medication causes of euvolemic hyponatremia that do not directly involvevasopressinor its receptors should be considered SIADH, but most authorities include medications as causes. Many medications have been linked to SIADH, but members of five drug classes are most often implicated: Analgesics (particularly opioids and nonsteroidal anti-inflammatory drugs) Antidepressants (particularly certain selectiveserotoninreuptake inhibitors,venlafaxine) Antiseizure drugs (particularlycarbamazepine) Antipsychotic drugs Cytotoxic drugs (particularlycyclophosphamideandvincristine). Not all drugs in each class appear to be equally causative ( Etiology reference ). 1.Shepshelovich D, Schechter A, Calvarysky B, et al: Medication-induced SIADH: distribution and characterization according to medication class.Br J Clin Pharmacol83(8):1801–1807, 2017. doi: 10.1111/bcp.13256 