LATE EVOLUTION OF SERUM IMMUNOREACTIVE PARATHYROID HORMONE, CALCITONIN AND PLASMA 25-HYDROXY CHOLECALCIFEROL CONCENTRATIONS IN VERY LOW BIRTHWEIGHT INFANTS

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Abstract
The plasma concentrations of 25-hydroxycholecalciferol (25-OH-CC), immunoreactive parathyroid hormone (iPTH) and calcitonin (iCT) were measured at the age of 30 and 66 days in 13 preterm neonates (birthweight: 970-1300 g). At the age of 30 days when all infants were fed only with breast milk (BM), serum iCT and iPTH levels were normal. During the 2nd month 7 infants were fed with BM only (control group) and 6 infants were supplemented with formula (supplemented group). At the age of 66 days, mean .+-. SD serum iPTH concentration was higher in the supplemented group than in the control group: 169 .+-. 79 vs. 60 .+-. 33 .mu.leq[microliter equivalents]/ml (P < 0.01). Serum iCT levels remained undetectable (< 150 pg/ml) in both groups. Plasma 25-OH-CC concentrations were normal and similar in both groups. Serum iPTH concentrations were positively correlated with P intake and negatively correlated with Ca intake from BM only. Secondary hyperparathyroidism evidently can be detected in very low birthweight infants supplemented with a formula, probably because of a P load or decreased intestinal Ca absorption.