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Low serum calcium and high parathyroid hormone levels in neonates fed 'humanized' cow's milk-based formula
B L Specker1, R C Tsang, M L Ho
1Department of Pediatrics, University of Cincinnati Medical Center, OH 45267-0541.
Insights
Late neonatal hypocalcemia may be linked to cow's milk-based formula's calcium-phosphorus ratio. Formula-fed infants showed lower ionized calcium and higher phosphate levels compared to breastfed infants.
Area of Science:
- Neonatal nutrition
- Pediatric endocrinology
- Biochemistry
Background:
- Late neonatal hypocalcemia is potentially linked to the calcium-phosphorus ratio in cow's milk-based infant formula.
- Previous suggestions lacked longitudinal data on ionized calcium and parathyroid hormone in neonates fed varying formula Ca/P ratios.
Purpose of the Study:
- To conduct a longitudinal study of ionized calcium and parathyroid hormone concentrations in neonates receiving formulas with different calcium-to-phosphorus (Ca/P) molar ratios.
- To compare these parameters between formula-fed and human milk-fed neonates.
Main Methods:
- Sixty-nine term neonates were studied up to 2 weeks of age.
- Formula-fed neonates were randomized to receive formulas with Ca/P molar ratios of 0.9, 1.2, or 1.4.
- Serum levels of ionized calcium, phosphate, and intact parathyroid hormone were measured on specific days.
Main Results:
- Formula-fed neonates had higher serum phosphate and lower ionized calcium levels on days 6 and 14 compared to human milk-fed neonates.
- Intact parathyroid hormone levels increased in formula-fed infants between days 2 and 6, while decreasing in human milk-fed infants.
- Serum parathyroid hormone on day 6 correlated with phosphorus intake in formula-fed neonates, but no significant differences were found among the formula groups.
Conclusions:
- Lower serum ionized calcium concentrations in neonates fed modern cow's milk-based formula may contribute to late neonatal hypocalcemia.
- The calcium-phosphorus ratio in current "humanized" formulas warrants further investigation regarding its impact on neonatal mineral balance.
Abstract:
We previously suggested that "late" neonatal hypocalcemia is related to a low calcium-phosphorus ratio of current cow's milk-based formula compared with human milk. However, there are no longitudinal studies of ionized calcium and parathyroid hormone concentrations in neonates receiving formulas with varying Ca/P ratios. Sixty-nine term neonates were studied through 2 weeks of age, and formula-fed neonates were randomized at birth to receive formula with molar ratios of 0.9, 1.2, or 1.4. Serum phosphate concentrations on days 2 and 6 of age were higher, and ionized calcium levels lower on days 6 and 14, in formula-fed vs human milk-fed neonates. Serum intact parathyroid hormone level increased between days 2 and 6 in formula-fed neonates compared with a decrease in human milk-fed neonates. Serum parathyroid hormone level on day 6 correlated with phosphorus intake among formula-fed neonates. No differences were noted in serum mineral or hormone levels among formula-fed groups. We speculate that the lowering of serum ionized calcium concentrations in neonates fed a modern "humanized" cow's milk formula may be a factor in late neonatal hypocalcemia.