normovolaemic, normal Na, slightly increased water
Last reviewed 08/2022
Causes of normovolaemic hyponatraemia include:- SIADH
- tumours
- chest/mediastinum e.g. mesothelioma, thymoma,bronchogenic carcinoma
- nonchest e.g. duodenal carcinoma, pancreatic carcinoma, nasopharyngeal carcinoma, ureteral/prostate carcinoma, uterine carcinoma,leukaemia
- CNS disorders
- mass lesions (tumours, abscesses, subdural hematoma)
- inflammatory diseases (encephalitis, meningitis, multiple sclerosis, systemic lupus, acute intermittent porphyria,)
- degenerative/demyelinative diseases (Guillain-Barré syndrome; spinal cord lesions)
- miscellaneous (head trauma, subarachnoid hemorrhage, acute psychosis, delirium tremens, pituitary stalk section, transphenoidal adenomectomy, hydrocephalus)
- drug induced
- stimulated AVP release (nicotine, phenothiazines, tricyclics)
- direct renal effects and/or potentiation of AVP antidiuretic effects (DDAVP, oxytocin, prostaglandin synthesis inhibitors)
- mixed or uncertain actions (e.g. ACE inhibitors, chlorpropamide, clofibrate, carbamazepine, clozapine, cyclophosphamide, 3,4-methylenedioxymethamphetamine ['Ecstasy'], omeprazole, serotonin reuptake inhibitors, vincristine)
- pulmonary
diseases
- infections (tuberculosis, acute bacterial and viral pneumonia, aspergillosis, empyema)
- mechanical/ventilatory (acute respiratory failure, COPD, positive pressure ventilation)
- tumours
- prolonged strenuous exercise (marathon, triathalon, ultramarathon, hot-weather hiking)
- idiopathic
- glucocorticoid deficiency
- hypothyroidism
- water intoxication – primary polydipsia, excess intravenous hypotonic fluids (2)
Reference:
- (1) hyponatraemia Treatment Guidelines 2007: Expert Panel Recommendations. American Journal of Medicine 2007; 120 (11);S1:S1-S21.
- (2) Reynolds RM, Seckl JR. Hyponatraemia for the clinical endocrinologist. Clin Endocrinol (Oxf). 2005;63(4):366-74