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Questions and Answers
Which function of magnesium is essential for the biological activity of ATP?
Which function of magnesium is essential for the biological activity of ATP?
What percentage of total body magnesium is typically found in bone?
What percentage of total body magnesium is typically found in bone?
Which type of food is considered a good source of magnesium?
Which type of food is considered a good source of magnesium?
Which physiological role is associated with magnesium's impact on the parathyroid glands?
Which physiological role is associated with magnesium's impact on the parathyroid glands?
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How much dietary magnesium is absorbed from the small intestine on average?
How much dietary magnesium is absorbed from the small intestine on average?
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What is the body's strategy for maintaining magnesium levels in blood?
What is the body's strategy for maintaining magnesium levels in blood?
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Which of the following is NOT a function of magnesium?
Which of the following is NOT a function of magnesium?
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Which demographic has higher magnesium requirements?
Which demographic has higher magnesium requirements?
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Which of the following is an early sign of low magnesium?
Which of the following is an early sign of low magnesium?
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What is the serum magnesium concentration that indicates marked intracellular depletion?
What is the serum magnesium concentration that indicates marked intracellular depletion?
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Which condition is a common cause of hypermagnesemia?
Which condition is a common cause of hypermagnesemia?
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What is the first step in managing hypermagnesemia?
What is the first step in managing hypermagnesemia?
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Which symptom is NOT associated with hypermagnesemia?
Which symptom is NOT associated with hypermagnesemia?
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What should be monitored carefully when administering magnesium in patients with renal impairment?
What should be monitored carefully when administering magnesium in patients with renal impairment?
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Which of the following treatments may be used for hypermagnesemia?
Which of the following treatments may be used for hypermagnesemia?
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Which magnesium-containing medication may contribute to hypermagnesemia?
Which magnesium-containing medication may contribute to hypermagnesemia?
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What are the clinical features associated with hypomagnesaemia?
What are the clinical features associated with hypomagnesaemia?
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What concentration defines hypomagnesaemia?
What concentration defines hypomagnesaemia?
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What effect does low serum magnesium have on parathyroid hormone secretion?
What effect does low serum magnesium have on parathyroid hormone secretion?
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Which condition is NOT a cause of magnesium deficiency?
Which condition is NOT a cause of magnesium deficiency?
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Which part of the kidney is most crucial for parathyroid hormone-regulated magnesium homeostasis?
Which part of the kidney is most crucial for parathyroid hormone-regulated magnesium homeostasis?
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How does hypermagnesaemia commonly present in patients?
How does hypermagnesaemia commonly present in patients?
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What is a common treatment for hypomagnesaemia?
What is a common treatment for hypomagnesaemia?
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What effect does magnesium have on parathyroid hormone secretion?
What effect does magnesium have on parathyroid hormone secretion?
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Study Notes
Magnesium
- Magnesium is an essential mineral for life, present in every cell type of every organism.
- Approximately 50% of total body magnesium is found in bone.
- 1% of magnesium is found in blood, and the body works hard to maintain constant blood levels.
- Good sources of magnesium include: green vegetables like spinach, legumes, nuts and seeds, whole grains, and hard water.
- Magnesium activates over 300 enzyme systems.
- Magnesium-dependent processes include: glycolysis, oxidative metabolism, and transmembrane transport of potassium and calcium.
- Low intracellular magnesium levels can affect electrical properties of cell membranes.
Magnesium Homeostasis
- Average dietary intake of magnesium: around 15 mmol per day, generally meeting recommended intake.
- Children, pregnant and lactating women have higher requirements.
- About 30% of dietary magnesium is absorbed from the small intestine, widely distributed to metabolically active tissues.
- Hypermagnesemia is uncommon, but can occur in renal failure.
- Hypomagnesemia symptoms are similar to hypocalcemia: impaired neuromuscular function, tetany, hyperirritability, tremor, convulsions, and muscle weakness.
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Parathyroid hormone (PTH) and magnesium have a complex relationship.
- Low magnesium levels stimulate PTH secretion.
- Very low magnesium levels can paradoxically block PTH secretion, potentially leading to hypocalcemia.
- This effect is mediated by activation of the alpha-subunits of heterotrimeric G-proteins, which mimic the calcium sensing receptor, and inhibit PTH secretion.
- PTH regulates magnesium homeostasis by modulating renal magnesium reabsorption, mainly in the distal convoluted tubule.
Magnesium Imbalance
Hypomagnesemia
- Definition: Serum magnesium concentration less than 1.8 mg/dL (0.70 mmol/L).
-
Causes::
- Inadequate intake and absorption of magnesium.
- Increased excretion due to hypercalcemia or medications (e.g., furosemide).
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Clinical features
- Often related to accompanying hypokalemia and hypocalcemia.
- Lethargy, tremor, tetany, seizures, and arrhythmias.
- Management: Magnesium replacement.
Causes of Magnesium Deficiency:
-
Dietary insufficiency compounded by:
- Intestinal malabsorption
- Severe vomiting
- Diarrhea
- Other causes of intestinal loss.
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Osmotic diuresis:
- Diabetes mellitus
- Prolonged use of diuretics, especially when dietary intake has been marginal.
- Nasogastric suction.
-
Cytotoxic drug therapy:
- Cisplatinum (impairs renal tubular reabsorption of magnesium)
- Treatment with the immunosuppressant: Cyclosporin
Symptoms of Magnesium Deficiency
-
Early signs:
- Nausea
- Vomiting
- Weakness
- Decreased appetite
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As deficiency worsens:
- Numbness
- Tingling
- Muscle cramps
- Seizures
- Muscle spasticity
- Personality changes
- Abnormal heart rhythms
Laboratory Diagnosis
- Serum magnesium concentration less than 0.7 mmol/L indicates marked intracellular depletion.
- Intracellular magnesium depletion can exist even with serum magnesium levels within the reference range.
Management
- Oral, intramuscular (IM) and intravenous (IV) regimens are available.
- Magnesium salts are contraindicated in significant renal impairment.
- Supplementation must be monitored carefully to avoid hypermagnesemia.
Hypermagnesemia
- Definition: Serum magnesium concentration greater than 2.6 mg/dL (1.05 mmol/L).
- Most common cause: Kidney failure, where the body can't properly regulate magnesium levels.
-
Other causes:
- Lithium therapy
- Hypothyroidism
- Addison’s disease
- Milk-alkali syndrome
- Drugs containing magnesium (e.g., laxatives, antacids)
- Familial hypocalciuric hypercalcemia
Symptoms of Hypermagnesemia
- Nausea
- Vomiting
- Neurological impairment
- Low blood pressure (hypotension)
- Flushing
- Headache
Management
- Primary management: Identify and stop the source of excess magnesium.
- Intravenous calcium: Helps reduce symptoms of impaired breathing, irregular heartbeat, hypotension, and neurological effects.
- Diuretics or water pills: May help remove excess magnesium.
- Dialysis: May be necessary for individuals with renal dysfunction or severe magnesium overdose who are experiencing kidney failure or persistent elevation in magnesium levels, despite other treatment.
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Description
Explore the crucial role of magnesium in the human body, including its sources, function, and homeostasis. This quiz covers how magnesium influences enzyme systems and the impact of low magnesium levels on health.
