The relation between serum preptin, myostatin, insulin, and also homeostatic model assessmentinsulin resistance were examined in pre-diabetes persons and newly diagnosed patients with overt type 2 diabetes mellitus. A total of 84 subjects were included in the study and assigned into three groups: normoglycemic participants (group 1=27), pre-diabetes (group 2=30), and T2DM (group 3=29). Serum insulin, preptin, and myostatin levels were measured with immunoradiometric assay (IRMA), enzyme-linked immunosorbent assay (ELISA), and chemiluminescent immunoassay (CLIA), respectively. Patients with T2DM had higher levels of preptin compared to normoglycemic (461. 25± 53. 90 vs. 407. 54± 54. 78, P<0. 001). Furthermore, these patients had elevated levels of myostatin compared with controls (2710. 60± 559. 09 vs. 2246. 37± 416. 40, P<0. 001). Preptin and myostatin both positively correlated with serum insulin (r=0. 369, P=0. 01, and r=0. 309, P=0. 04, respectively). However, no significant association was found between serum preptin and myostatin levels. Stepwise multiple regression analysis showed that insulin was affected more by preptin, with only a trivial contribution from myostatin. Serum preptin and myostatin levels increase in prediabetic subjects and even further in type 2 diabetic patients. The correlation between preptin and insulin evolves when pre-diabetes or overt type 2 diabetes develops. Moreover, serum myostatin increases in association with insulin and not HOMA-IR in diabetic conditions.