Hyperaldosteronism

Why should I check serum magnesium level in my patient with hypokalemia in need of potassium replacement?

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

Short answer: Potassium and magnesium are highly intertwined in their physiological roles and magnesium is critical for renal retention of potassium.

Hypomagnesemia increases the release of renin from the kidney, leading to elevated levels of angiotensin II, which stimulates the adrenal cortex to secrete aldosterone. 1,2 The resulting secondary hyperaldosteronism contributes to refractory hypokalemia through increased sodium reabsorption via epithelial sodium channels (ENaC) in the distal nephron.  Increased sodium reabsorption in turn increases the expression and activity of the renal outer medullary potassium (ROMK) channels, which increases potassium secretion into the tubular lumen.1,3 Interestingly, magnesium also directly inhibits ROMK channels which, in the setting of hypomagnesemia, further leads to potassium loss.1,4

Parenthetically, most patients with mild to moderate hypomagnesemia are asymptomatic or have non-specific symptoms such as lethargy, muscle weakness or cramps. So don’t rely on symptoms to decide who should have their serum magnesium checked in the setting of hypokalemia. 5

Last, hypomagnesemia is not uncommon. It is found in 3-10% of general population, 10-30% of patients with type 2 diabetes, 10-60% of hospitalized patients and over 65% of those in the intensive care unit.5   What’s more concerning is that hypomagnesemia is also associated with an elevated risk of death from any cause and death from cardiovascular diseases.5

So, don’t forget to check serum magnesium level in your patient with hypokalemia in need of potassium replacement!

Bonus Pearls: Did you know that many drugs such as proton pump inhibitors (PPIs), thiazide and loop diuretics, aminoglycosides and chemotherapeutic agents are associated with magnesium wasting and hypomagnesemia, while sodium-glucose cotransporter-2 (SGLT2) inhibitors may be associated with increased renal magnesium reabsorption? 5

Contributed by Andy Wu, PhD, Medical Student, St. Louis University Medical School, St. Louis, Missouri

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References

  1. Huang CL, Kuo E. Mechanism of hypokalemia in magnesium deficiency. J Am Soc Nephrol. 2007 Oct;18(10):2649-52. doi: 10.1681/ASN.2007070792. Epub 2007 Sep 5. PMID: 17804670. https://pubmed.ncbi.nlm.nih.gov/17804670/
  2. AlShanableh Z, Ray EC. Magnesium in hypertension: mechanisms and clinical implications. Front Physiol. 2024 Apr 10;15:1363975. doi: 10.3389/fphys.2024.1363975. PMID: 38665599; PMCID: PMC11044701. https://pubmed.ncbi.nlm.nih.gov/38665599/
  3. Valinsky WC, Touyz RM, Shrier A. Aldosterone, SGK1, and ion channels in the kidney. Clin Sci (Lond). 2018 Jan 19;132(2):173-183. doi: 10.1042/CS20171525. PMID: 29352074; PMCID: PMC5817097. https://pubmed.ncbi.nlm.nih.gov/29352074/
  4. Rodan AR, Cheng CJ, Huang CL. Recent advances in distal tubular potassium handling. Am J Physiol Renal Physiol. 2011 Apr;300(4):F821-7. doi: 10.1152/ajprenal.00742.2010. Epub 2011 Jan 26. PMID: 21270092; PMCID: PMC3074996. https://pubmed.ncbi.nlm.nih.gov/21270092/
  5. Touyz RM, de Baaij JHF, Hoenderop JGJ. Magnesium Disorders. N Engl J Med. 2024 Jun 6;390(21):1998-2009. doi: 10.1056/NEJMra1510603. PMID: 38838313. https://pubmed.ncbi.nlm.nih.gov/38838313/

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!

Why should I check serum magnesium level in my patient with hypokalemia in need of potassium replacement?

Is there a connection between urinary tract infections (UTIs) and hypokalemia?

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

Although we don’t usually think of UTIs being associated with electrolyte abnormalities, there seems to be a connection between UTI—particularly pyelonephritis—and hypokalemia in adults, possibly related to the impairment of renal potassium resorption due to tubular injury.1

A 2020 study of over 80,000 hospitalized patient found a significantly higher rate of hypokalemia (10%) in patients with UTI (identified based on ICD9 codes) vs non-UTI patients (4%, O.R. 2.3, 95% C.I. 2.2-2.4). This association was independent of patients’ comorbidities and medications. Among patients with UTI, recurrent UTI was associated with hypokalemia (O.R. 1.1, 95% C.I. 1.1-1.2). Unfortunately, no attempt was made to distinguish cystitis from pyelonephritis. The authors reported that in “several patients”, the urinary potassium secretion was increased.  

The association between pyelonephritis and hypokalemia was first reported back in the 1950s and was initially referred to as “potassium losing nephropathy”. 2 It turns out that some of these cases might have had underlying primary hyperaldosteronism (Conn’s) and perhaps pyelonephritis unmasked this condition.  Later, cases of urinary potassium wasting with probable pyelonephritis in the absence of excessive aldosterone excretion were also reported, with resolution of potassium wasting with treatment of the infection in some instances.3,4  

So it looks like the association between pyelonephritis and hypokalemia may be real! Next time you see hypokalemia in a patient with pyelonephritis, don’t be surprised! The corollary: watch for hypokalemia in your patient with pyelonephritis!

Bonus Pearl: Did you know that prevention of potassium loss with spironolactone treatment in pyelonephritis has been reported, suggesting a possible role for aldosterone despite lack of hyperaldosteronism.3

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References

  1. Shen AL, Lin HL, Lin HC, et al. Urinary tract infection is associated with hypokalemia: a case control study. BMC Urology 2020;20:108. Urinary tract infection is associated with hypokalemia: a case control study | BMC Urology | Full Text (biomedcentral.com)
  2. Eastham RD, McElligott M. Potassium-losing pyelonephritis. BMJ 1956; :898-89. Potassium-losing pyelonephritis. – Abstract – Europe PMC
  3. Gerstein AR, Franklin SS, Kleeman CR, et al. Potassium losing pyelonephritis:response to spironolactone. Arch Intern Med 1969;123:55-57. Potassium Losing Pyelonephritis: Response to Spironolactone | JAMA Internal Medicine | JAMA Network
  4. Jones NF, Cantab MB, Mills IH, et al. Reversible renal potassium loss with urinary tract infection. Am J Med 1964;37:305-310. REVERSIBLE RENAL POTASSIUM LOSS WITH URINARY TRACT INFECTION – PubMed (nih.gov)

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University,their affiliate 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!

 

Is there a connection between urinary tract infections (UTIs) and hypokalemia?