• Five full-term infants with birth weights appropriate for gestational age presented with hypocalcemic tetany at 5 to 9 days of age. All infants had been fed Similac 20, a cow milk formula. Initial mean serum calcium (Ca), phosphorus (P), and magnesium (Mg) levels of the tetanic infants were 6.8, 9.5, and 1.6 mg/dL, respectively. The mean serum parathyroid hormone (PTH) level was elevated at 79 μLEq/mL (adult normal values, ≤57 μLEq/mL). Following restoration of normocalcemia with Ca supplements, feeding was reinstituted with Similac 20 in two infants and Similac PM 60/40 in three infants. Serum biochemical and hormonal values were compared with those of 18 exclusively breast-fed infants followed up from three weeks to six months and 14 Similac 20–fed full-term infants followed up from one week to six months. In tetanic infants, serum Ca concentrations became elevated (10.4±0.05 mg/dL; mean±SEM) by six weeks (vs 9.2±0.3 mg/dL in breast-fed infants) (P<.001) and serum Mg concentrations (2.26 ± 0.01 mg/dL) by four weeks (vs 1.92±0.07 mg/dL in breast-fed infants) (P<.01). Mean serum P concentrations declined progressively. Mean serum PTH concentrations were elevated and ranged from 74 to 143 μLEq/mL at two to 16 weeks (vs mean 28 to 35 μLEq/mL in breast-fed infants (P<.0001). In 14 formula-fed–nontetanic full-term infants, serum PTH concentrations were intermediate between formula-fed–tetanic and breast-fed infants, mean serum Ca concentrations ranged from 10.2 to 10.4 mg/dL, and mean serum P concentrations declined from 8.3 to 7.1 mg/dL. We speculate that acute hypocalcemic tetany in the study infants was induced by the relatively high P load in cow milk formulas (vs human milk); with the continued P load, secondary hyperparathyroidism continued, maintaining P, Ca, and Mg homeostasis.
Pankaja S. Venkataraman, Reginald C. Tsang, Frank R. Greer, Akihiko Noguchi, Peter Laskarzewski, Jean J. Steichen. Late Infantile Tetany and Secondary Hyperparathyroidism in Infants Fed Humanized Cow Milk FormulaLongitudinal Follow-up. Am J Dis Child. 1985;139(7):664–668. doi:10.1001/archpedi.1985.02140090026018