IGF1 and bronchopulmonary dysplasia: As shown in Figures 3, the concentrations of IGF-1 in serum samples from infants with different severity of BPD were always different on days 1, 7, 14, and 28, and infants diagnosed with severe BPD were significantly associated with a lower level of IGF-1 than those with mild BPD (P < 0.05).