4th Year Medicine: Mineral Disorders Quiz

4th Year Medicine: Laboratory Medicine Course - Mineral Disorders

• Course Focus: Mineral disorders
• Instructor: Assistant Prof. Jehad Tayyeb
• Date: 2023
• Learning Objectives: Students will be able to clarify normal and abnormal plasma levels of magnesium, sodium, potassium, and calcium; explain disorders associated with abnormal mineral levels; and outline laboratory tools for estimating mineral concentrations.

Magnesium (Mg)

• Abundance: Fourth most abundant cation (Mg²⁺) in the body
• Total Body Content: 21-28 grams
• Normal Serum Mg: 1.7-2.5 mg/dL
• Distribution:
  • 53% stored in bone
  • 46% in muscles and soft tissues
  • 1% extracellularly in blood and red blood cells (RBCs)

Magnesium (Mg) Functions

• Muscle and Nerve Function: Important for proper function of muscles and nerves
• ATP Complex: Forms a complex with ATP, acting as a cofactor for enzymes, transporters, and nucleic acids
• Metabolism Support: Crucial for the metabolism of sodium, potassium, calcium, vitamin C, and phosphorus
• Electrolyte Balance: Maintains electrolyte balance
• Anti-stress: Has anti-stress properties

Hypomagnesemia

• Definition: Clinically significant deficiency of less than 1.2 mg/dL
• Renal Causes:
  • Hypercalcemia
  • Tubular disorders in the kidney
  • Hyperaldosteronism
  • Diuretics
• Extrarenal Causes:
  • Malnutrition
  • Malabsorption, chronic diarrhea, or laxative abuse
  • Increased cell uptake of Mg
  • Increased storage in bone after parathyroidectomy

Hypermagnesemia

• Rarity: Rare, usually in patients with renal failure taking Mg-containing drugs

Sodium

• Plasma Levels: 132-144 mmol/L
• Daily Requirements: 5-15 grams daily, primarily as sodium chloride (NaCl)
• Excretion: About 95% of sodium excreted in urine

Sodium Distribution and Functions

• Distribution: About one-third of total body sodium is in the skeleton, while most is in extracellular fluids.
• Associated Minerals: Primarily associated with chloride and bicarbonate
• Acid-Base Balance: Important in regulating acid-base balance in body fluids
• Fluid Regulation: Maintains body fluid levels and protects against excessive fluid loss
• Muscle and Cell Function: Important for normal muscle irritability and cell permeability

Hypernatremia

• Causes:
  • Rapid administration of sodium salt
  • Hyperactivity of the adrenal cortex (Cushing's disease)
  • Administration of corticotrophin (ACTH) and cortisone
  • Dehydration (diabetes insipidus)

Hyponatremia

• Symptoms: Muscular cramps, headache, and nausea
• Causes:
  • Adrenocortical insufficiency
  • Chronic renal failure
  • Liver cirrhosis
  • Congestive heart failure
  • Excessive gastrointestinal fluid loss (severe diarrhea)
  • Excessive sweating

Potassium

• Plasma Levels: 3.6-4.8 mmol/L
• Distribution and Functions:
  • Principal intracellular cation, also important in the extracellular fluid
  • Influences muscle activity, especially cardiac muscles
  • Important for acid-base balance
  • Essential for metabolic functions (e.g., protein synthesis, glycogenesis, glycogenolysis)

Hyperkalemia

• Causes:
  • Renal failure
  • Dehydration
  • Adrenal insufficiency (Addison's disease)
• Symptoms:
  • Central nervous and cardiac symptoms (bradycardia, poor heart sounds)
  • Peripheral vascular collapse and cardiac arrest
  • Mental confusion, numbness, weakness of respiratory muscles, and paralysis

Hypokalemia

• Causes:
  • Chronic diseases with malnutrition
  • Gastrointestinal losses (vomiting, diarrhea)
  • Overactivity of the adrenal cortex (Cushing's syndrome)
  • Diuretic administration (e.g., acetazolamide, chlorothiazide)
• Symptoms:
  • Muscle weakness, irritability, paralysis, tachycardia

Calcium

• Distribution: 99% stored in bone and teeth; 1% intracellular (primarily in mitochondria and endoplasmic reticulum); 0.1% extracellular (plasma calcium 9-11 mg/dL)

Calcium Functions

• Bone and Tooth Structure: Major mineral in bone and teeth
• Nerve Impulse Transmission: Essential for nerve impulse transmission
• Muscle Contraction: Important for muscle contraction
• Enzyme Activation: Required for activation of certain enzymes
• Blood Clotting: Essential for blood clotting

Hypocalcemia

• Definition: Decrease of plasma calcium level below 9 mg/dL
• Causes:
  • Hypoparathyroidism
  • Vitamin D deficiency
  • Low serum albumin
  • Hypomagnesemia
  • Medullary carcinoma of the thyroid
  • Chronic renal insufficiency
  • Malabsorption
  • Alcoholism

Hypercalcemia

• Definition: Increase of plasma calcium level above 11 mg/dL
• Causes:
  • Primary hyperparathyroidism
  • Secondary hyperparathyroidism (e.g., in renal failure)
  • Vitamin D toxicity
  • Tumors producing parathyroid hormone (PTH)-related proteins
  • Bone metastasis

Laboratory Tools

• Spectrophotometer: Measures the amount of light absorbed by a sample. Used to determine mineral levels.
• Routine Automated Biochemistry Analyzers: Machines that process many samples for mineral levels quickly.
• Blood Tests: Use blood samples to measure mineral concentration.
• Urine Tests: Analyze urine samples to determine mineral levels (24-hour urine tests are crucial for evaluating dietary intake or loss.)