Plasma gastrin and somatostatin levels in newborn infants receiving supplementary formula feeding.

Plasma gastrin and somatostatin concentrations were measured by radioimmunoassay in exclusively formula-fed infants and in breast-fed infants receiving supplementary formula during the first five postnatal days. Infants exclusively formula fed had a progressive increase in mean plasma gastrin concentration from 109 +/- 42 pmol/l (mean +/- SD) on the first day to 236 +/- 103 pmol/l on the fifth day after birth (p = 0.0001). Breast-fed infants receiving supplementary formula had similar hormone concentrations as formula-fed infants of corresponding postnatal age and they also had a significant increase in hormone levels from the first to the fifth day (p = 0.0001). A positive relationship was found between gastrin concentration and ingested milk volume: Rs = 0.51, n = 105, p = 0.0001. The high gastrin concentrations most probably reflect enhanced hormonal release from the gastrin-producing cells in response to increasing volumes of milk ingested by the infant. The mean plasma somatostatin concentration on the first day after birth was 18 +/- 6 pmol/l. No significant change occurred during the first five postnatal days, independent of feeding type.