Our expression analysis revealed an upregulation of three different key components of the IGF/insulin pathway (Igf1r, Irs2 and Insr) in IUGR rats compared to shams at 5, 20 and 40 dpp, respectively, suggesting a possible influence of this system both on SC number and testosterone production by LC during the catch-up growth phase occurring in IUGR rat testis from 20 dpp. The gene discussed is IGF1; the disease is fetal growth restriction.