That isn't the case. There is a characteristic array of skin conditions associated with diabetes , but psoriasis is rarely mentioned among them. Psoriatics, on the other hand, tend to have fewer skin infections than the general population, most often opportunistic fungi on the lesions. Since psoriasis is not a disease of extreme insulin resistance, it is unlikely that merely elevated insulin or glucose is the cause. Even if it were so, then psoriasis would be expected to appear in conditions of hyperinsulemia.
Elevated insulin appears naturally in some populations, and in at least one common condition.
During normal pregnancy, a state similar to insulin resistance arises as the mother's body metabolism changes to meet the increased demands. If psoriasis were caused by insulin resistance, it would be expected to worsen during pregnancy. Just the opposite happens. A mother with psoriasis often finds that it improves during pregnancy, and often later flares again after the baby is born. This is more readily explained by her immune system shifting from being suppressed so as not to reject the fetus, to then delivering all the needed antibodies for the newborn baby's undeveloped immune protection.