This study was conducted to evaluate the effect of cyadox on endocrine hormones and growth factor in pigs. Forty-eight crossbred pigs (35±7 days) were randomly allotted to one of four treatments, with six replicate pens per treatment and two pigs per pen. Pigs were offered one of four diets including a control diet or the control diet supplemented with cyadox at either 25, 50 or 100 mg/kg for 8 weeks. Growth performance data and serum were collected every 2 weeks. Serum epidermal growth factor (EGF), insulin, thyroid hormones (tri-iodothyronine (T3) and thyroxine (T4)), and cortisol concentrations were determined. Results indicated that average daily gain (ADG) and gain/food ratio increased linearly and quadratically with increasing cyadox levels. The treatment containing cyadox at 50 mg/kg improved ADG by proportionately 0·241 and food efficiency by 0·25 ( P<0·05) during the entire experiment. In our study, EGF (during weeks 4 to 8), insulin (during weeks 4 to 6), thyroid hormones (in week 4) concentrations increased quadratrically ( P<0·05) and the cortisol concentrations (in week 4) decreased linearly ( P<0·01) with increasing supplementation of cyadox. Pigs given 50 mg/kg cyadox diet had greater ( P<0·05) EGF concentrations than pigs on other diets throughout the experiment. An increase (proportionately 0·22) in serum insulin concentrations in cyadox group was also observed ( P<0·05) in week 4. From week 2 to week 4, the T4 concentrations of cyadox group increased by 50% ( P<0·05). Moreover, feeding cyadox to pigs elevated their serum T3 concentrations ( P<0·05) in the 4th week and 8th week. The cortisol concentrations of cyadox group were decreased ( P<0·05) in week 4. These results suggest that cyadox improve pig performance by altering concentrations of peripheral metabolic hormones and growth factor.