What electrolyte abnormalities occur with hypomagnesemia?
Hypomagnesemia causes modest hypocalcemia. This is presumed to be due to bone resistance to parathyroid hormone.
Hypomagnesemia causes treatment-resistant hypokalemia. Of note, many causes of hypomagnesemia also independently cause hypokalemia (diuretics, alcoholism, and chronic diarrhea, etc.), so some hypokalemia is not due to the hypomagnesemia, but rather due to the process causing hypomagnesemia. It is estimated that 50% of patients with hypokalemia also have a magnesium deficiency, and replacing potassium alone will not correct the hypokalemia. Magnesium binds the inner surface of the ROMK channel of the cortical collecting duct, limiting potassium efflux. With magnesium depletion, this inhibition of potassium efflux is lost, causing increased kidney potassium loss