{"entity":{"id":"siadh","kind":"term","name":"SIADH (syndrome of inappropriate antidiuretic hormone secretion)","aka":["SIADH","Syndrome of inappropriate antidiuresis","SIAD","Syndrome of inappropriate ADH","Hyponatraemia in cancer","Hyponatremia in cancer"],"tldr":"SIADH is when the body makes too much of the hormone that holds on to water, so the blood becomes too dilute and its sodium falls. It is most often seen with small-cell lung cancer and with some cancer medicines, and can cause nausea, headache and confusion.","summary":"Castillo and colleagues (Oncologist 2012) describe hyponatraemia as a common electrolyte abnormality in oncology, usually caused in people with cancer by SIADH, which develops more often with small-cell lung cancer than with other malignancies. SIADH may come from ectopic production of arginine vasopressin by the tumour or from effects of anticancer and palliative medicines on vasopressin production or action. Treatment depends on symptom severity, speed of onset and volume status: hypertonic saline for acute symptomatic cases, fluid restriction for chronic asymptomatic hyponatraemia, and drugs such as the V2-receptor antagonist tolvaptan when restriction is not enough.\n\nThe Society for Endocrinology emergency guidance grades sodium as mild (130 to 135 mmol/L), moderate (125 to 129) and profound (below 125), and symptoms as severe (vomiting, seizures, reduced consciousness, cardiorespiratory arrest) or moderately severe (nausea without vomiting, confusion, headache), noting that the clinical picture may not match the sodium level.","asOf":"2026-11-11","links":[{"label":"Castillo et al., Diagnosis and management of hyponatremia in cancer patients (Oncologist 2012)","url":"https://europepmc.org/article/MED/22618570"},{"label":"Ball et al., Society for Endocrinology Endocrine Emergency Guidance: emergency management of severe symptomatic hyponatraemia in adult patients (Endocr Connect 2016)","url":"https://europepmc.org/article/PMC/PMC5314809"}],"tags":["supportive-care-gaps-2026-11"],"related":[],"cancers":["sclc"],"sections":[],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"provenance":{"editedBy":"OnCo supportive care gap fill (CDC, NHSN, SHEA, Society for Endocrinology, ESMO, MASCC, ASCO, ASTCT, NCI PDQ, Europe PMC)","editedOn":"2026-11-11"},"category":"Side effects"},"route":"/terms/siadh/","neighbours":{"cancer":[{"id":"sclc","kind":"cancer","name":"Small-cell lung cancer","route":"/cancers/sclc/"}]}}