Hypocalcemia
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Basics
Description
- Hypocalcemia is defined as a total plasma calcium level <8.7 mg/dL:
- Ionized calcium may be normal and, therefore, have no clinical manifestations
- Normal total serum calcium concentrations are 8.7–10.5 mg/dL
- Normal ionized calcium levels are 4.64–5.28 mg/dL
Etiology
- Incidence in the general population is 0.6%
- Mechanism:
- From either increased loss of calcium from the circulation or decreased entry into the circulation
- Intravascular calcium circulates in 3 forms:
- Bound to proteins (mainly albumin): 45–50%
- Bound to complexing ions (citrate, phosphate, carbonate): 5–10%
- Ionized (free) calcium (physiologically active form): 45–50%
- Serum levels of calcium are primarily controlled by 3 hormones:
- Parathyroid hormone (PTH)
- Decrease in calcium levels leads to an increase in PTH secretion (increasing bone resorption, renal absorption, intestinal absorption, and urinary phosphate excretion)
- Vitamin D (1,25-dihydroxyvitamin D):
- Decrease in calcium level activates vitamin D (increasing bone resorption and intestinal absorption)
- Calcitonin:
- Causes a direct inhibition of bone resorption with increased calcium levels
- Hypoalbuminemia – the most common cause:
- Each 1 g/dL decrease in serum albumin decreases protein-bound serum calcium by 0.8 mg/dL
- Ionized (free) calcium levels do not change
Pediatric Considerations
- Children have higher values of normal calcium (9.2–11 mg/dL)
- Neonatal hypocalcemia: Total serum calcium concentrations <7.5 mg/dL or serum-ionized calcium levels <4 mg/dL
- Symptoms of hypocalcemia in infancy:
- Hyperactivity, jitteriness
- Tachypnea
- Apneic spells with cyanosis
- Vomiting
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Basics
Description
- Hypocalcemia is defined as a total plasma calcium level <8.7 mg/dL:
- Ionized calcium may be normal and, therefore, have no clinical manifestations
- Normal total serum calcium concentrations are 8.7–10.5 mg/dL
- Normal ionized calcium levels are 4.64–5.28 mg/dL
Etiology
- Incidence in the general population is 0.6%
- Mechanism:
- From either increased loss of calcium from the circulation or decreased entry into the circulation
- Intravascular calcium circulates in 3 forms:
- Bound to proteins (mainly albumin): 45–50%
- Bound to complexing ions (citrate, phosphate, carbonate): 5–10%
- Ionized (free) calcium (physiologically active form): 45–50%
- Serum levels of calcium are primarily controlled by 3 hormones:
- Parathyroid hormone (PTH)
- Decrease in calcium levels leads to an increase in PTH secretion (increasing bone resorption, renal absorption, intestinal absorption, and urinary phosphate excretion)
- Vitamin D (1,25-dihydroxyvitamin D):
- Decrease in calcium level activates vitamin D (increasing bone resorption and intestinal absorption)
- Calcitonin:
- Causes a direct inhibition of bone resorption with increased calcium levels
- Hypoalbuminemia – the most common cause:
- Each 1 g/dL decrease in serum albumin decreases protein-bound serum calcium by 0.8 mg/dL
- Ionized (free) calcium levels do not change
Pediatric Considerations
- Children have higher values of normal calcium (9.2–11 mg/dL)
- Neonatal hypocalcemia: Total serum calcium concentrations <7.5 mg/dL or serum-ionized calcium levels <4 mg/dL
- Symptoms of hypocalcemia in infancy:
- Hyperactivity, jitteriness
- Tachypnea
- Apneic spells with cyanosis
- Vomiting
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