How does impaired GI magnesium absorption cause hypomagnesemia?

Updated: Oct 30, 2020
  • Author: Tibor Fulop, MD, PhD, FACP, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Impaired gastrointestinal magnesium absorption is a common underlying basis for hypomagnesemia, especially when the small bowel is involved, due to disorders associated with malabsorption, chronic diarrhea, or steatorrhea, or as a result of bypass surgery on the small intestine. Because there is some magnesium absorption in the colon, patients with ileostomies can develop hypomagnesemia.

An emerging association is, described with increasing frequency, the association with proton pump inhibitors (PPIs), widely used to reduce gastric acid secretion,  [80, 81, 82, 91] presumably due to decreased gastrointestinal absorption. As of March 2011, the US Federal Drug Administration (FDA) issued a safety warning on PPIs, including a recommendation to periodically monitor serum levels.

In a population-based case-control study of 366 patients hospitalized with hypomagnesemia and 1,464 matched controls, Zipursky and colleagues found that current use of PPIs was associated with a 43% increased risk of hypomagnesemia (adjusted odds ratio [OR], 1.43; 95% confidence index [CI] 1.06–1.93). The increased risk was significant among patients receiving diuretics, (adjusted OR, 1.73; 95% CI 1.11–2.70) but not among those who were not receiving diuretics (adjusted OR, 1.25; 95% CI 0.81–1.91).  [93]

HSH is a rare autosomal-recessive disorder characterized by profound hypomagnesemia associated with hypocalcemia.  [94] Pathophysiology is related to impaired intestinal absorption of magnesium  [95] accompanied by renal magnesium wasting as a result of a reabsorption defect in the DCT. Mutations in the gene coding for TRPM6, a member of the transient receptor potential (TRP) family of cation channels, have been identified as the underlying genetic defect.  [22, 23, 24]

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