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Syndrome of inappropriate antidiuretic hormone

Last reviewed: 6 Apr 2025
Last updated: 25 Mar 2025

Summary

Definition

History and exam

Key diagnostic factors

  • absence of hypovolemia
  • absence of hypervolemia
  • absence of signs of adrenal insufficiency or hypothyroidism
  • nausea
  • vomiting
  • altered mental status
  • headache
  • seizure
  • coma
Full details

Other diagnostic factors

  • no history of recent diuretic use
Full details

Risk factors

  • age >50 years
  • pulmonary conditions (e.g., pneumonia)
  • nursing home residence
  • postoperative state
  • malignancy
  • medication associated with SIADH induction
  • central nervous system (CNS) disorder
  • endurance exercise
Full details

Diagnostic tests

1st tests to order

  • serum sodium
  • serum osmolality
  • serum BUN
  • urine osmolality
  • urine sodium
Full details

Tests to consider

  • diagnostic trial with normal saline infusion
  • serum uric acid
  • fractional excretion of sodium
  • fractional excretion of urea
  • serum TSH
  • serum cortisol level
  • serum arginine vasopressin (AVP)
Full details

Treatment algorithm

ACUTE

severe symptoms

mild to moderate symptoms

asymptomatic with sodium ≥125 mEq/L

ONGOING

persistence of chronic SIADH

Contributors

Authors

Nephrologist

Arizona Kidney Disease and Hypertension Center

Phoenix

AZ

Disclosures

MD declares that she has no competing interests.

Professor Emeritus of Medicine

Division of Nephrology

University of Arizona

Tucson

AZ

Disclosures

YHL is an author of a reference cited in this topic.

Peer reviewers

Assistant Professor

Nephrology

Yale University

New Haven

CT

Disclosures

MG declares that she has no competing interests.

Associate Director

Nephrology

Washington Hospital Center

Washington

DC

Disclosures

JHV declares that she has no competing interests.

Consultant Nephrologist

Renal Unit

Lancashire Teaching Hospitals

Fulwood

Preston

UK

Disclosures

LS declares that he has no competing interests.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Gross P. Clinical management of SIADH. Ther Adv Endocrinol Metab. 2012 Apr;3(2):61-73.Full text  Abstract

Spasovski G, Vanholder R, Allolio B, et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Eur J Endocrinol. 2014 Mar;170(3):G1-47.Full text  Abstract

Ball S, Barth J, Levy M, et al. Society for Endocrinology endocrine emergency guidance: emergency management of severe symptomatic hyponatraemia in adult patients. Endocr Connect. 2016 Sep;5(5):G4-6.Full text  Abstract

Verbalis JG, Goldsmith SR, Greenberg A, et al. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013 Oct;126(10 suppl 1):S1-42.Full text  Abstract

Ellison DH, Berl T. The syndrome of inappropriate antidiuresis. N Engl J Med. 2007 May 17;356(20):2064-72.

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.
  • Syndrome of inappropriate antidiuretic hormone images
  • Differentials

    • Pseudohyponatremia
    • Hypovolemia
    • Cerebral salt-wasting
    More Differentials
  • Guidelines

    • Emergency management of severe symptomatic hyponatraemia in adult patients
    • Clinical practice guideline on diagnosis and treatment of hyponatraemia
    More Guidelines
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