Hypomagnesiemia Flashcards
Q: What does hypomagnesemia mean?
A: Hypomagnesemia refers to lower than normal magnesium levels in the blood, typically below 1 mEq/L.
Q: How much magnesium does an average adult have in their body?
A: An average adult has about 25 grams of magnesium in their body.
Q: Where is most of the body’s magnesium stored?
A: About half is stored in the bones, and most of the other half is within cells.
Q: What fraction of total body magnesium is found in the extracellular space?
A: About 1% of the total magnesium is in the extracellular space.
Q: How is magnesium distributed in the extracellular space?
A: About 20% is bound to proteins like albumin, and 80% is filterable by the kidneys.
Q: How much magnesium gets reabsorbed at different parts of the nephron?
A: 30% at the proximal convoluted tubule, 60% at the ascending loop of Henle, and 5% at the distal convoluted tubule.
Q: What causes increased excretion of magnesium in urine?
A: When the nephron fails to reabsorb magnesium, or due to the use of loop and thiazide diuretics.
Q: How do loop and thiazide diuretics affect magnesium reabsorption?
A: They make the lumen less positively charged, reducing magnesium’s electrochemical gradient and causing more magnesium to be excreted.
Q: What is Gitelman syndrome?
A: A genetic mutation in the Na-Cl cotransporters in the distal tubule affecting magnesium reabsorption.
Q: How can prolonged malnutrition cause hypomagnesemia?
A: Not enough magnesium is consumed.
Q: How can medications like proton pump inhibitors cause hypomagnesemia?
A: They interfere with magnesium absorption in the gastrointestinal tract.
Q: How does uncontrolled diabetes mellitus lead to hypomagnesemia?
A: Increased glucose in the nephron attracts water, increasing urine flow and reducing magnesium reabsorption time.
Q: What is hungry bone syndrome?
A: Increased bone formation after thyroid or parathyroid surgery leading to consumption of blood magnesium by osteoblasts.
Q: How does alcoholism contribute to hypomagnesemia?
A: Poor diet leads to low magnesium intake and alcohol increases renal excretion of magnesium.
Q: Why is hypomagnesemia commonly associated with hypokalemia?
A: Conditions causing hypomagnesemia, like diarrhea and diuretics, also cause hypokalemia and magnesium affects potassium channel function.
