Objective To study the expression of sex hormone-binding globulin(SHBG),insulin signaling pathway and glucose transporter in placenta of pregnant women with gestational diabetes mellitus(GDM),and to explore its role in the pathogenesis of GDM. Methods A total of 10 full-term and non-obese(BMI<25 kg/m2)pregnancy women diagnosed with GDM and 10 normal pregnant cases were recruited for the study. Placental tissues were collected respectively. The expression of protein and mRNA of SHBG and insulin signal transduction(IRS-1,ISR-2,PI3K p85α)and glucose transporter proteins(GLUT-1,GLUT-3,GLUT-4)in placental tissue were detected by real-time PCR and Western blotting. Pearson and linear regression analysis were used to evaluate the correlation among the related indicators. Results In the placental tissue of non-obese women,there existed a decrease(P<0.05)in the expression of protein and mRNA of SHBG with a concurrent a decrease(P<0.05)in the expression of protein and mRNA of GLUT-4 in GDM women compared with normal controls. Furthermore ,a decrease(P<0.05)of GLUT-3 and IRS-1 protein expression with lower(P<0.05)IRS-2 mRNA expression was also observed in placental tissue from GDM patients. No changes were found in PI3K p85α and GLUT-1 at both protein and mRNA levels(P>0.05). Results of linear correlation analysis showed that there were positive correlations between SHBG mRNA and IRS-2 mRNA(P<0.05),SHBG mRNA and PI3K p85α mRNA(P<0.05),and SHBG mRNA and GLUT-4 mRNA(P<0.05). There was also a remarkable positive correlation between IRS-2 mRNA and GLUT-4 mRNA(P<0.01). There existed negative correlations between IRS-1 mRNA and PI3K p85α mRNA(P<0.05),and IRS-1 mRNA and GLUT-3 mRNA(P<0.05). There existed a remarkable positive correlation between IRS-2 mRNA and GLUT-1 mRNA(P<0.01). Conclusion The defective receptors of insulin signaling pathway are present in GDM placental tissue. Decreased expression of SHBG may be involved in the regulation insulin signaling ,leading to a concomitant decrease expression of relevant insulin signaling components in placental tissue ,implying insulin resistance and developing GDM finally.