FGF21 and Insulin resistance: Chavez et al compared the serum FGF21 in thin, fat, fasting blood sugar impaired and diabetic patients and found that people with type II diabetes had higher serum FGF21 compared to other groups, linking this to the status of insulin resistance.[16] Also, in a study by Kralisch et al, the mean concentration of serum FGF21 in patients with type II diabetes mellitus was 2.1 times higher compared to the healthy controls.[17] The level of this factor decreases in type I diabetes as it is synthesized in the liver and pancreas and people with type I diabetes have impaired pancreas function.