Recent clinical and experimental evidences suggest that sex steroids protect from insulin resistance associated with diabetes. Therefore, we have assessed the influence of E2 and/or P4 on insulin sensitivity by euglicaemic-hyperinsulinaemic clamp in ovariectomized streptozotocin-induced diabetic rats, focusing on key proteins of insulin signaling in skeletal muscle. Although low plasma levels of E2 (days 6 and 11) increased Glut-4 plasma membrane content and subsequent improved insulin sensitivity, they could not fully reverse hyperglycaemia negative effects on p85alpha-IRS-1 association and IRS-1 content during 11 days. However, high plasma levels of E2 (day 16) could reverse hyperglycaemia effects not only on Glut-4 plasma membrane content but also on p85alpha-IRS-1 association and IRS-1 protein content level. In contrast, P4 treatment only improved insulin sensitivity when its plasma concentration was low (days 6 and 11) and its effects were not associated with any proteins study in this paper. The combined therapy had a synergic effect on insulin sensitivity when their plasma levels were low (day 6) or high (day 16), that could be associated with Glut-4 plasma membrane content modulation, p85alpha-IRS-1 association and IRS-1 amount. These new findings improve our understanding of biochemical basis of insulin resistance due to hyperglycaemia and could open up new possibilities of treatment in uncontrolled type 1 DM.