SIADH

What is the role of measuring serum uric acid level in my patient with hyponatremia suspected of having syndrome of inappropriate antidiuretic hormone secretion (SIADH)?

FA Manian MD, MPH, , , , , , , , , , , Leave a comment

The utility of checking serum uric acid (SUA) in hyponatremia primarily stems from the fact that it helps distinguish SIADH from volume contraction as the cause of hyponatremia.1 Whereas hyperuricemia commonly accompanies volume contraction, hypouricemia is found in the majority (70%) of patients with SIADH.2 This finding is caused by increased urinary excretion of SUA in patients with SIADH.3

There are several potential mechanisms for the association of SIADH with hypouricemia. First, the expanded vascular volume in these patients enhances UA clearance by decreasing its reabsorption, as supported by improved UA serum levels in SIADH patients on fluid restriction.4 Of note, UA normalization with fluid restriction is more pronounced in chronic SIADH patients compared to healthy individuals acutely volume overloaded via treatment with synthetic ADH (i.e. desmopressin).5 This may be due to the fact that, unlike endogenous ADH, desmopressin is a selective agonist of vasopressin 2 receptors (V2R), promoting water reabsorption in the collecting duct without binding to vasopressin 1 receptors (V1R), which promotes UA secretion and inhibits UA reabsorption in the proximal tubule.5,6  To make things worse, there is also evidence that chronic hyponatremia induced by SIADH can directly promote UA excretion!7

Last, keep in mind that salt-wasting disease, a less common cause of hyponatremia, may also be associated with hypouricemia. However, in contrast to patients with SIADH, UA excretion remains high and serum UA levels remain low in these patients even after their hyponatremia is corrected. 8

Bonus Pearl: Did you know that tolvaptan, a selective ADH (V2R) antagonist, has been shown to be effective in raising serum sodium and UA levels in SIADH patients with the caveat that its chronic use may also cause hyperuricemia? 9,10

Contributed by Stella Hoft, PhD, Medical Student, St. Louis University Medical School, St. Louis, Missouri

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References

  1. Liamis G, Christidis D, Alexandridis G, Bairaktari E, Madias NE, Elisaf M. Uric acid homeostasis in the evaluation of diuretic-induced hyponatremia. J Investig Med. 2007 Jan;55(1):36-44. doi: 10.2310/6650.2007.06027. PMID: 17441410. https://journals.sagepub.com/doi/10.2310/6650.2007.06027?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed
  2. Decaux G, Musch W. Clinical laboratory evaluation of the syndrome of inappropriate secretion of antidiuretic hormone. Clin J Am Soc Nephrol. 2008 Jul;3(4):1175-84. doi: 10.2215/CJN.04431007. Epub 2008 Apr 23. PMID: 18434618. https://journals.lww.com/cjasn/abstract/2008/07000/clinical_laboratory_evaluation_of_the_syndrome_of.38.aspx
  3. Li R, Wu B, Han M, Li M, Yang X, Zhang J, Zhang Y, Liu Y. Uric Acid Metabolic Disorders in Pituitary-Target Gland Axis. Diabetes Metab Syndr Obes. 2024 Feb 7;17:661-673. doi: 10.2147/DMSO.S448547. PMID: 38343584; PMCID: PMC10859102. https://www.dovepress.com/uric-acid-metabolic-disorders-in-pituitary-target-gland-axis-peer-reviewed-fulltext-article-DMSO
  4. Beck LH. Hypouricemia in the syndrome of inappropriate secretion of antidiuretic hormone. N Engl J Med. 1979 Sep 6;301(10):528-30. doi: 10.1056/NEJM197909063011005. PMID: 460306. https://www.nejm.org/doi/abs/10.1056/NEJM197909063011005
  5. Decaux G, Namias B, Gulbis B, Soupart A. Evidence in hyponatremia related to inappropriate secretion of ADH that V1 receptor stimulation contributes to the increase in renal uric acid clearance. J Am Soc Nephrol. 1996 May;7(5):805-10. doi: 10.1681/ASN.V75805. PMID: 8738818. https://journals.lww.com/jasn/abstract/1996/05000/evidence_in_hyponatremia_related_to_inappropriate.23.aspx
  6. Taniguchi K, Tamura Y, Kumagai T, Shibata S, Uchida S. Stimulation of V1a receptor increases renal uric acid clearance via urate transporters: insight into pathogenesis of hypouricemia in SIADH. Clin Exp Nephrol. 2016 Dec;20(6):845-852. doi: 10.1007/s10157-016-1248-x. Epub 2016 Mar 2. PMID: 26935049. https://link.springer.com/article/10.1007/s10157-016-1248-x
  7. Decaux G, Prospert F, Soupart A, Musch W. Evidence that chronicity of hyponatremia contributes to the high urate clearance observed in the syndrome of inappropriate antidiuretic hormone secretion. Am J Kidney Dis. 2000 Oct;36(4):745-51. doi: 10.1053/ajkd.2000.17623. PMID: 11007676. https://www.ajkd.org/article/S0272-6386(00)08495-X/ppt
  8. Momi J, Tang CM, Abcar AC, Kujubu DA, Sim JJ. Hyponatremia-what is cerebral salt wasting? Perm J. 2010 Summer;14(2):62-5. doi: 10.7812/TPP/08-066. PMID: 20740122; PMCID: PMC2912080. https://www.thepermanentejournal.org/doi/10.7812/TPP/08-066
  9. Nagamine T. Uric acid levels with tolvaptan treatment for syndrome of inappropriate antidiuretic hormone secretion. Endocrine. 2024 Mar;83(3):826-827. doi: 10.1007/s12020-023-03612-3. Epub 2023 Nov 20. PMID: 37982946. https://link.springer.com/article/10.1007/s12020-023-03612-3
  10. Bondanelli M, Aliberti L, Gagliardi I, Ambrosio MR, Zatelli MC. Long-term low-dose tolvaptan efficacy and safety in SIADH. Endocrine. 2023 Nov;82(2):390-398. doi: 10.1007/s12020-023-03457-w. Epub 2023 Jul 28. PMID: 37507553; PMCID: PMC10543144. https://link.springer.com/article/10.1007/s12020-023-03457-w

Disclosures/Disclaimers: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

What is the role of measuring serum uric acid level in my patient with hyponatremia suspected of having syndrome of inappropriate antidiuretic hormone secretion (SIADH)?

How common is hyponatremia in patients with Covid-19 and what’s its significance?  

FA Manian MD, MPH, , , , , , , , , , , , , , , , , , , , Leave a comment

Hyponatremia has been reported between 20% and 35% of patients hospitalized for Covid-19, 1-5 with low serum sodium levels on admission often associated with progression to severe illness, mechanical ventilation, increased length of stay and death.1,2,4,5

A 2023 retrospective multicenter study involving over 2,600 hospitalized Covid-19 patients (between February 2020 and August 2022) found hyponatremia in 34.2%: Mild (Na 131-134 mmol/L) 25.1%, moderate (Na 126-130 mmol/L) 7.5% and severe (<126 mmol/L) 1.8%.3 There was a significant association between male sex at birth, hypertension, chronic kidney disease, immunosuppressives, thiazide diuretics and hyponatremia.3

Similarly, another retrospective study of hospitalized Covid-19 patients found an association between hyponatremia and several common chronic diseases, such as diabetes, hypertension, ischemic heart disease, chronic liver disease and chronic kidney disease.4 It’s important to note that since older age has also been found to be a risk factor for hyponatremia in Covid-19, the independent contribution of these conditions to hyponatremia is unclear.3

As with many other infectious diseases, the mechanism of hyponatremia in patients with Covid-19 likely has multiple causes, including hypovolemia, syndrome of inappropriate anti-diuretic hormone secretion (SIADH), diuretic use and corticosteroid deficiency, particularly in the critically ill. 1-4  

Interestingly, a study performed early in the pandemic (March 2020) found that the majority (57%)  of hospitalized Covid-19 patients with hyponatremic were euvolemic and that the administration of isotonic saline to such patients was independently associated with increased hospital mortality (cause unclear).2 The authors suggested closer attention to the volume status of Covid-19 patients with hyponatremia (eg, through closer attention to the jugular venous pressure on physical exam) before considering treatment with isotonic saline.

Last, Covid-19 may be associated with hyponatremia during the post-discharge period as well.  An intriguing 2024 study found nearly 25% of patients with Covid-19 developed hyponatremia (<135 mmol/L) during the 1-year follow-up period after discharge with most not reported to have hyponatremia during their index hospitalization.5 In the same study, hyponatremia was associated with older age, male sex, diabetes, hypertension, heart failure, previous invasive ventilatory support and increased rate of readmission.5

Bonus Pearl: Did you know that there is an inverse relationship between interleukin-6, a key pro-inflammatory cytokine, and plasma sodium levels in Covid-19 and that this association may be stronger than that of other viral or bacterial respiratory infections?2  

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References

  1. Ayus JC, Klantar-Zadeh K, Tantisattamo E, et al. Is hyponatremia a novel marker of inflammation in patients with Covid-19? Nephrol Dial Transplant 2023;38:1921-24. Is hyponatremia a novel marker of inflammation in patients with COVID-19? – PubMed (nih.gov)
  2. Pazos-Guerra M, Ruiz-Sanchez JG, Perez-Candel X, et al. Inappropriate therapy of euvolemic hyponatremia, the most frequent type of hyponatremia in SARS-CoV-2 infection, is associated with increased mortality in COVID-19 patients. Front Endocrinol 2023; 14:1227058. Inappropriate therapy of euvolemic hyponatremia, the most frequent type of hyponatremia in SARS-CoV-2 infection, is associated with increased mortality in COVID-19 patients – PubMed (nih.gov)
  3. De Haan L, ten Wolde, Beudel M, et al. What is the aetiology of dynatreaemia in COVID-19 and how is this related to outcomes in patients admitted during earlier and later COVID-19 waves? A multicentre, restrospective observational study in 11 Dutch hospitals. BMJ Open 2023;13:e075232. Original research: What is the aetiology of dysnatraemia in COVID-19 and how is this related to outcomes in patients admitted during earlier and later COVID-19 waves? A multicentre, retrospective observational study in 11 Dutch hospitals – PMC (nih.gov)
  4. Rehman F, Rehan ST, Rind BJ, et al. Hyponatremia causing factors and its association with disease severity and length of stay in Covid-19 patients: A retrospective study from tertiary care hospital. Medicine 2023; 102:45(e35920) Hyponatremia causing factors and its association with disease severity and length of stay in COVID-19 patients: A retrospective study from tertiary care hospital – PubMed (nih.gov)
  5. Biagetti B, Sanchez-Montalva A, Puig-Perez A, et al. Hyponatremia after COVID-19 is frequent in the first year and increases re-admissions. Scientific Reports 2024:14:595. Hyponatremia after COVID-19 is frequent in the first year and increases re-admissions – PubMed (nih.gov)

 

Disclosures/Disclaimers: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

How common is hyponatremia in patients with Covid-19 and what’s its significance?