In the PDE-induced IUGR model, at GD20, the comprehensive ranking in male rat cartilage was RPL4, RPL5, ACTB, SDHA, GAPDH, HPRT1, 18S, GUSB (Figure 4K); at PW6, it was RPL5, SDHA, RPL4, GAPDH, ACTB, 18S, GUSB, HPRT1 (Figure 4L); at PW12, it was RPL4, RPL5, 18S, SDHA, GAPDH, HPRT1, GUSB, ACTB (Figure 4M). The gene discussed is HPRT1; the disease is fetal growth restriction.