Serum Calcium and Phosphorus in Pediatrics
Key Points
- Essential minerals for bone mineralization and cellular function
- Age-dependent reference ranges
- Inverse relationship in serum levels
- Critical for growth and development
Age-Specific Reference Ranges
- Total Calcium:
- Newborns: 8.0-11.3 mg/dL
- Infants: 9.0-11.0 mg/dL
- Children: 8.8-10.8 mg/dL
- Adolescents: 8.5-10.5 mg/dL
- Phosphorus:
- Newborns: 4.8-8.2 mg/dL
- Infants: 4.5-7.5 mg/dL
- Children: 3.7-5.8 mg/dL
- Adolescents: 2.9-5.4 mg/dL
Calcium Assessment
Forms and Distribution
- Total Calcium Components:
- Ionized (free) calcium: 50%
- Protein-bound: 40%
- Complexed calcium: 10%
- Factors Affecting Measurement:
- Albumin levels
- pH changes
- Binding proteins
- Sample handling
Measurement Considerations
- Corrected Calcium Calculation:
- Formula: Corrected Ca = Measured Ca + 0.8(4.0 - Albumin)
- When to use: Albumin < 4.0 g/dL
- Limitations and alternatives
- Ionized Calcium Testing:
- Gold standard for assessment
- Special handling required
- pH-adjusted results
Phosphorus Evaluation
Physiological Aspects
- Distribution:
- Intracellular: 70%
- Bone: 29%
- Extracellular: 1%
- Regulatory Factors:
- PTH effects
- Vitamin D influence
- FGF-23 regulation
- Dietary intake
Clinical Significance
- Growth Impact:
- Bone mineralization
- Cellular energy metabolism
- DNA/RNA synthesis
- Cell membrane composition
- Daily Requirements:
- Infants: 100-200 mg/day
- Children: 400-1200 mg/day
- Adolescents: 1200-1600 mg/day
Clinical Applications
Diagnostic Approach
- Hypercalcemia Evaluation:
- Primary hyperparathyroidism
- Malignancy
- Williams syndrome
- Vitamin D toxicity
- Hypocalcemia Assessment:
- Vitamin D deficiency
- Hypoparathyroidism
- DiGeorge syndrome
- Nutritional deficiency
Phosphorus Disorders
- Hyperphosphatemia:
- Renal failure
- Tumor lysis syndrome
- Vitamin D toxicity
- Rhabdomyolysis
- Hypophosphatemia:
- Rickets
- Refeeding syndrome
- X-linked hypophosphatemia
- Malabsorption
Management Strategies
Monitoring Protocols
- Frequency of Testing:
- Acute disorders: Daily
- Chronic conditions: Weekly-Monthly
- Maintenance: Every 3-6 months
- Additional Investigations:
- Urinary calcium/creatinine ratio
- Tubular reabsorption of phosphate
- Bone-specific alkaline phosphatase
- 25-OH Vitamin D levels
Therapeutic Interventions
- Calcium Disorders:
- Acute management protocols
- Supplementation strategies
- Dietary modifications
- Monitoring parameters
- Phosphorus Imbalances:
- Replacement guidelines
- Dietary counseling
- Binder therapy
- Long-term management
Further Reading
