INS and diabetes mellitus: In adults with T2D, plasma IGF-1 and C-peptide levels have been reported to be positively correlated.21 In a cohort of low-birth-weight children without diabetes, a higher IGF-1 level at 5 years was associated with higher insulin secretion (insulinogenic index) at 8 years.22 Together, these data suggest a potential role of IGF-1 in preserving beta cell function.