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Phosphorous Imbalances

Phosphorous:
  • Normal Serum Phosphorous : 2.5–4.5 mg/dL
  • Role: ATP production , bone strength, cell membranes, DNA & RNA synthesis
  • Has Inverse relation with  Calcium (High  Phosphorus → Low Calcium)
  • PTH → lowers Phosphorus ,
  • Vitamin D → Increases both Ca & phosphate 
  • Sources: Dairy, meat, nuts, fish, pumpkin, beans, whole grains

Important

  • Low phosphate → Low ATP → weak and slow cells.
  • High phosphate → Low calcium → twitchy and tight muscles.

Hyperphosphatemia refers to serum phosphate level above 4.5 mg/dL (1.45 mmol/L).

Causes

  • Decreased  Renal excretion: CKD, AKI
  • Tumor lysis syndrome (post-chemotherapy)
  • Excess phosphorus-rich foods, phosphate enemas/laxatives
  • Hypoparathyroidism (↓ PTH → ↓ phosphate excretion)

Pathophysiology

      High phosphate causes calcium–phosphorus precipitation → hypocalcemia + soft tissue calcification→ Organ damage

Clinical Signs 

(Symptoms are often from secondary hypocalcemia.)

  • Tetany, muscle cramps, paresthesia, seizures – due to hypocalcemia
  • Dysrhythmias, possible cardiomyopathy
  • Calcium–phosphate deposits in skin, eyes, blood vessels, organs → Organ damage

Management

  1. Treat the causes (renal disease, tumor lysis, hormonal imbalance)
  2. Diet restriction: Limit dairy, organ meats, fish/poultry, nuts, seeds, colas
  3. Phosphate binders:
    • Calcium carbonate / calcium acetate / sevelamer
    • Take with meals for best effect
  4. Avoid phosphate products, increase hydration, treat Hypocalcemia
  5. Severe cases: Hemodialysis
  6. IV insulin + glucose → shifts both K⁺ and phosphate into cells

Hypophosphatemia refers to serum phosphorus (phosphate) level below 2.5 mg/dL 

Key: Low Phosphate → High Calcium [Inverse relationship]

Causes

  • Poor dietary phosphate intake 
  • Low vitamin D  
  • Malabsorption – GI issues or alcohol-induced malabsorption
  • Phosphate loss from hyperparathyroidism or phosphate-binding antacids
  • Phosphate shift into cells due to respiratory alkalosis or  insulin

Pathophysiology:

Hypophosphatemia reduce ATP production, causing impaired energy metabolism and cell function.

Signs & Symptoms

  • Weak muscles, especially breathing muscles (check airway)
  • Weak heart – Low BP, weak pulse
  • Weak bones – fractures
  • Confusion, irritability, seizures – (severe ATP depletion → activate rapid response emergency team and ensure safety)
  • Bleeding, Infection risk (impairs ATP-dependent platelet & WBC functions)
  • <1 mg/dL + symptoms = MEDICAL EMERGENCY

Treatment

  1. Stop phosphate binders like aluminum hydroxide antacids, calcium acetate, calcium carbonate, sevelamer, lanthanum.
  2. Mild: Oral phosphate supplements + Vitamin D (enhances absorption).
  3. Severe:  IV phosphate given slowly to avoid complications 
  4. After phosphate correction, watch for hypocalcemia → tingling, cramps, tetany, seizures.
  5. Encourage high-phosphate foods like Dairy, fish, nuts, meat, pumpkin, whole grains
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