Phosphate Imbalances: Causes and Manifestations

Phosphate

Primary anion in ICF
- Essential to function of muscle, red blood cells, and nervous system
- Involved in acid-base buffering system, ATP production, cellular uptake of glucose, and metabolism of carbohydrates, proteins, and fats
- Serum levels controlled by parathyroid hormone
- Maintenance requires adequate renal functioning
- Reciprocal relationship with calcium
Hyperphosphatemia
- High serum PO43- caused by
  - Acute kidney injury or chronic kidney disease
  - Chemotherapy
  - Excess intake of phosphate or vitamin D
  - Hypoparathyroidism
- Manifestations
  - Neuromuscular irritability and tetany (hypocalcemia)
  - Calcified deposits in soft tissue like, arteries, skin, kidneys, and corneas (can cause organ dysfunction)
  - Numbness and tingling in extremities and region around mouth
  - Hyperreflexia, muscle cramps
  - Tetany, seizures
- Management
  - Identify and treat underlying cause
  - Restrict foods and fluids containing phosphorus
  - Oral phosphate-binding agents
  - Volume expansion and forced diuresis
  - Correct any hypocalcemia
  - Hemodialysis
Hypophosphatemia
- Low serum PO₄^3- caused by
  - Malnourishment/malabsorption/diarrhea
  - Use of phosphate-binding antacids
  - Inadequate replacement during parenteral nutrition
- Manifestations
  - CNS depression
  - Muscle weakness and pain
  - Respiratory and heart failure
  - Rickets and osteomalacia
  - Cardiac problems (dysrhythmias, heart failure)
  - Osteomalacia, rickets
  - Rhabdomyolysis
- Management
  - Oral supplementation
  - Ingestion of foods high in phosphorus
  - IV administration of sodium or potassium phosphate

Phosphate Imbalances: Causes and Manifestations
Hyperphosphatemia (PO₄³⁻ >4.4 mg/dL [1.42 mmol/L])	Hypophosphatemia (PO₄³⁻ <2.4 mg/dL [0.78 mmol/L])
Cause
Renal failure	Malabsorption syndromes
Phosphate enemas (e.g., Fleet Enema)	Chronic diarrhea
Excessive ingestion (e.g., phosphate-containing laxatives)	Malnutrition, vitamin D deficiency
Rhabdomyolysis	Parenteral nutrition
Tumor lysis syndrome	Chronic alcoholism
Thyrotoxicosis	Phosphate-binding antacids
Hypoparathyroidism	Diabetic ketoacidosis
Sickle cell anemia, hemolytic anemia	Hyperparathyroidism
Hyperthermia	Refeeding syndrome
	Respiratory alkalosis

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