The relationship between IGF-I and -II concentrations and body composition at birth and over the first 2 months

BACKGROUND: Insulin-like growth factor (IGF)-I and -II play an important role in prenatal growth. During the first 2 months from birth, body fat doubles, and rapid weight gain during this time increases future risk of cardiometabolic disease. The aim of this study was to determine whether IGF measurements at birth associate with body composition and the trajectory of its changes in the first 2 months. METHODS: Umbilical cord IGF-I and -II concentrations were measured in term infants. Air displacement plethysmography was performed at birth and 2 months. Fat mass (FM) and fat-free mass (FFM) were corrected for infant length (L) to FM/L-3 and FFM/L-2, respectively. RESULTS: In 601 (317 male) infants, IGF-I concentrations at birth were associated with FM/L-3 and FFM/L-2 Z-scores at birth (R-2 = 0.05 and 0.04, respectively, P < 0.001), and IGF-II concentrations were associated with FFM/L-2 Z-scores at birth (R-2 = 0.01, P = 0.02). Lower IGF-I concentrations were weakly associated with increases in FM/L-3 Z-scores over the first 2 months (R-2 = 0.01, P = 0.003). CONCLUSION: IGF-I concentrations at birth are associated with adiposity and lean mass at birth and inversely with the trajectory of FM accumulation over the first 2 months. IGF-I measurements only account for a small amount of the variance in these measures.