Serum calcitonin response to administration of calcium in newborn infants during exchange blood transfusion.

In 25 newborn infants, 30 "exchange" transfusions were performed. Pre-exchange serum calcitonin concentrations of newborn infants were higher than those of normal adults and of donor blood used for exchange transfusion. A gradual decline of serum calcitonin concentrations was observed with increasing postnatal age. Serum calcium and magnesium concentrations were inversely related to serum calcitonin concentrations. Newborn infants had significant elevations of serum calcitonin values within a few minutes after the administration of calcium. Gestationally younger infants (less than or equal to 33 weeks) had significantly more pronounced and swifter elevations of serum calcitonin concentrations after calcium administration than gestationally more mature infants (less than 33 weeks). We speculate that calcitonin may be an important "fetal hormone" and that increased calcitonin concentrations may relate to the pathogenesis of neonatal hypocalcemia.