Use of insulin-like growth factor I (IGF-I) and IGF-binding protein measurements to monitor feeding of premature infants

W. Jackson Smith, Louis E. Underwood, Lynette Keyes, David R. Clemmons

Research output: Contribution to journalArticlepeer-review

67 Scopus citations

Abstract

To determine whether peptides of the insulin-like growth factor (IGF) system might be useful indicators of nutritional adequacy in premature infants, we studied 50 premature (25-34 weeks gestation) infants prospectively to define the relationship between nutrient intake and serum concentrations of IGF-I, IGF-binding proteins-2 (IGFBP-2), and IGFBP-3. Each infant was monitored for at least 2 weeks. Nutrient intake was quantified from daily logs; weight was determined daily, and measurements of IGF-I, IGFBP-2, and IGFBP-3 in serum were made twice weekly. Serum IGF-I correlated strongly with length of gestation, increasing 4.03 ± 0.95 ng/mL for each additional week of gestation (P < 0.0001) and 0.36 ± 0.07 ng/mL day each day since birth (P < 0.0001). A higher intake of calories increased IGF-I by 0.07 W± 0.01 ng/mL for each calorie per kg ingested over the previous 3 days (P < 0.0001). IGF-I increased quadratically as protein intake increased. For each change of 1% in calories as protein squared, IGF-I increased 0.36 ± 0.11 ng/mL (P < 0.0001). Serum IGFBP-3 concentrations also correlated with length of gestation, increasing 25.06 ± 11.83 μg/L·wk (P = 0.035) and 4.14 ± 1.33 μg/·day since birth (P = 0.003). Unlike IGF-I, variation in the amount of protein supplied did not change IGFBP-3. As calorie intake increased, IGFBP-3 increased by 0.54 ± 0.17 μg/L for each calorie per kg consumed over the previous 3 days (P: 0.0015). In contrast to IGF-I and IGFBP-3, IGFBP-2 declined as the length of gestation increased (56.12 ± 16.92 ng/mL·week; P = 0.001) and with each additional day of life (7.57 ± 2.44 ng/mL·day; P = 0.003). Dietary protein, the predominant regulator of IGFBP-2, caused a decrease of 33.22 ± 9.00 ng/mL with each percent increase in dietary calories as protein (P < 0.0003). Calorie intake had less effect on IGFBP-2 than protein intake. These results indicate that each of the three peptides studied is regulated in premature infants by nutritional intake, and that their regulatory patterns are qualitatively similar to those observed in older individuals. Measurements of these peptides in premature infants may be useful indicators of nutritional status and adequacy of nutrient intake.

Original languageEnglish
Pages (from-to)3982-3988
Number of pages7
JournalJournal of Clinical Endocrinology and Metabolism
Volume82
Issue number12
DOIs
StatePublished - 1997

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Endocrinology
  • Clinical Biochemistry
  • Biochemistry, medical

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