What type of GI disorders lead to hypomagnesemia?
GI losses occur with diarrhea and vomiting. Lower GI losses cause more hypomagnesemia due to a higher magnesium content in the secretions (up to 15 mEq/L with lower GI compared with 1 mEq/L with upper GI losses). This is particularly important in malabsorptive syndromes.
In acute pancreatitis, lipase metabolizes triglycerides to free fatty acids. The fatty acids are capped by carboxyl group with a charge of –1. The carboxyl group binds cations, specifically calcium and magnesium. The carboxyl complex precipitates out of solution lowering the calcium and magnesium. This process is called saponification .
Proton pump inhibitors can cause severe hypomagnesemia. The mechanism has not been fully worked out, but it appears that renal magnesium handling is intact and most attention is focused on active magnesium absorption by TRPMP6 channels in the terminal ileum and colon. It is hypothesized that the higher pH of intestinal secretions with proton pump inhibitor (PPI) decreases TPRM6/7 affinity for magnesium. It resolves with discontinuation of the drug but returns with rechallenge.
Primary intestinal hypomagnesemia is a rare congenital hypomagnesemic condition. Patients will typically also have renal magnesium wasting, because the molecular defect in the apical magnesium channel, TRPM6, is also found in the kidney. The condition has variable inheritance. It typically presents in infancy and early childhood but can present in young adults.