The objective of this study was to examine the effects of triiodothyronine (T₃) implantation on the performance of physiology of cultured great sturgeon (Huso huso). Three treatments with 5 fish for each treatment were considered. The experimental treatments included: control (capsules containing cocoa butter alone), low level of T₃ (T₁; 1 mg T₃/kg body weight + cocoa butter), and high level of T₃ (T₁₀; 10 mg T₃/kg body weight+ cocoa butter). The capsules containing hormones and cocoa butter were intraperitoneally implanted to 3-year-old pre-vitellogenic stage female fish (mean initial body weight 6999.7±100.9 g) every 6 weeks over a six month period  from January 2009 to June 2010. The serum levels of some hormone (T₃, cortisol, ACTH) and biochemical parameters (glucose, cholesterol and calcium) were determined at the initial time and three weeks after each implantation. Growth indices (WG, SGR and CF) were determined at the end of the experiment. The results showed that fish treated with the high and low T₃ doses produced significant changes in thyroid hormone levels (P<0.05). Serum cortisol was significantly higher in T₃- implanted fish than in control fish (P<0.05). Serum glucose and calcium concentrations were significantly greater in fish treated with the high T₃ doses compared to the other two experimental groups (P<0.05). Significant differences were observed in serum ACTH and cholesterol concentrations among treatments in the last and second sampling time, respectively (P<0.05). Final weight was the highest in T₁-implanted fish; intermediate in those implanted the high T₃ dose, and lowest in controls (P<0.05). These results indicated that the long-term implantations of T₃ hormone influence the physiological parameters of great sturgeon and promote the somatic growth in a physiological dose.