Disorders of magnesium metabolism
1. Unlike other electrolytes that are primarily reabsorbed in the proximal tubule, magnesium is primarily reabsorbed in the thick ascending limb of the loop of Henle.
2. Conditions associated with increased urine output predispose to low magnesium. This includes diuretics, IV fluids, and poorly controlled diabetes.
3. Low magnesium causes other electrolytes to fall. Hypomagnesemia can cause hypokalemia and hypocalcemia.
4. Hypermagnesemia is usually only found with renal failure, either acute or chronic.
5. Increased magnesium causes decreased deep tendon reflexes and can ultimately cause muscle weakness and respiratory arrest.