Use of plasma somatomedin-C/insulin-like growth factor I measurements to monitor the response to nutritional repletion in malnourished patients

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Abstract
Changes in plasma somatomedia-C/insulin-like growth factor I (Sm-C/IGF-I) concentrations are a sensitive indicator of the anabolic response of normal human volunteers to alterations in nutritional intake. To determine if measurement of this peptide could be used to monitor the response to nutritional repletion in malnourished patients, six patients were studied while receiving nutritional support for periods of 10–16 days. Plasma Sm-C/IGF-I increased from a mean basal level of 0.67 ± 0.15 U/ml (±1 SD) to a peak of 1.80 ± 0.44 U/ml on day 10, then declined to a concentration of 1.28 ± 0.49 U/ml by day 16. All patients entered positive nitrogen balance by day 2 and nitrogen accretion continued throughout the study. Changes in serum concentrations of prealbumin, transferrin, and retinol-binding protein were compared to changes in Sm-C/IGF-I during nutritional support. Prealbumin increased to a posttreatment mean of 121 ± 23% of control by the end of the study (p > 0.05, NS). Likewise, there was minimal change in retinol-binding protein, a peak value of 118 ± 21% of control being reached by day 12 of treatment (p > 0.05, NS). Transferrin also showed minimal change, increasing to a mean value of 110% ± 13% of control by day 12 (p > 0.05, NS). Measurement of plasma Sm-C/IGF-I concentrations appears to be a much more sensitive index of acute directional changes in nutritional status than other plasma proteins commonly used to monitor nutritional responses. The increase of Sm-C/IGF-I correlated temporally with entry into positive nitrogen balance. The results indicate that measurement of plasma Sm-C/IGF-I offers promise as a useful means for monitoring the response of acutely ill patients to nutritional intervention.