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Serum-ionized calcium in mexican protein-energy malnourished children
S Frenk1, B Pérez-Ortíz, T Murguía
1Unidad de Genética de la Nutrición, Genética Nutricional, Universidad Nacional Autónoma de México (UNAM)-Instituto Nacional de Pediatría (INP), Mexico City, Mexico.
Insights
Ionized calcium levels remain normal in children with severe protein-energy malnutrition (PEM). This study confirms that even with low total calcium, the crucial ionized form is maintained during illness and recovery.
Area of Science:
- Pediatric Endocrinology
- Nutritional Biochemistry
- Clinical Chemistry
Background:
- Severe primary protein-energy malnutrition (PEM) in children can lead to hypocalcemia, primarily due to reduced protein-bound calcium.
- Ultrafilterable calcium (Ca(U)), which includes ionized calcium, has been considered unaffected in PEM.
- Ionized calcium is the physiologically active form of calcium and a key component of Ca(U).
Purpose of the Study:
- To investigate whether ionized calcium concentration remains normal in infants with severe PEM.
- To test the hypothesis that ionized calcium is maintained despite variations in total serum calcium levels in infantile PEM.
Main Methods:
- Blood samples were collected from 18 infants with marasmic PEM and 6 with kwashiorkor.
- Ionized calcium was measured using ion-selective electrodes in serum aliquots.
- Total calcium, protein, albumin, and phosphate levels were also analyzed.
Main Results:
- Ionized serum calcium concentrations were within normal limits for most samples, including during nutritional recovery.
- Total calcium, protein, albumin, and phosphate levels were generally decreased but normalized during recovery.
- Two initial samples showed exceptions to the normal ionized calcium levels.
Conclusions:
- Ionized calcium serum concentration is maintained within normal limits in severe infantile protein-energy malnutrition.
- This finding highlights the body's mechanisms for preserving physiologically critical calcium levels even in severe malnutrition.
Background:
Hypocalcemia occurring in children with severe primary protein-energy malnutrition (PEM) has previously been shown to merely reflect a reduction in the protein-bound fraction of serum calcium. On the other hand, ultrafilterable, i.e., nonprotein bound calcium (Ca(U)), remains unaffected. The aim of the present investigation was to test the hypothesis that in infantile PEM, ionized calcium, which represents the major and physiologically most important component of Ca(U), is also kept within a normal concentration, whatever the total serum calcium levels.
Methods:
Three milliliters of peripheral venous blood were obtained on admission and periodically afterward from 18 fasting marasmic infants and 6 children with the edematous form of PEM (kwashiorkor). Ionized calcium was determined in 125 microL aliquots of blood serum with ion-selective electrodes. The measurement of related elements and molecules was carried out with customary laboratory procedures.
Results:
On admission, as well as during the ensuing stages of nutritional recovery, ionized serum calcium exhibited a normal concentration, with the exception of two initial samples. Total calcium, total protein, albumin, and inorganic phosphate concentrations were decreased in a variable degree according to the clinical type, ascending to normal levels during recovery.
Conclusions:
Ionized calcium serum concentration remains within normal limits in severe infantile PEM.
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