At a usage level of 250 mg/week, Sustanon provides basically only a high level of testosterone replacement therapy. Individuals with low testosterone may see a marked improvement, but many with mid-normal or high natural testosterone will see little added effect at this dosage level. Yet, Sustanon is suppressive of the hypothalamus and pituitary at this dosage and will largely shut down natural testosterone production while being used. So, this dosage has relatively little of the benefits of most steroid cycles, but shares the adverse side effect of suppressed testosterone production.
Fifty 2- to 16- yr old pony stallions were randomly assigned to one of five treatments: Group 1, controls (no treatment); Group 2, mg/kg stanozolol weekly for 13 treatments; Group 3, mg/kg stanozolol every 3 wk for 5 treatments; Group 4, mg/kg boldenone undecylenate every 3 wk for 5 treatments; and Group 5, boldenone undecylenate weekly for 13 treatments. Mean plasma testosterone levels for Groups 2, 4, and 5 were elevated over controls (P<) at 2, 8, and 9 wk, respectively. Testosterone levels for ponies in Group 3 did not differ from controls (P>). There were no differences in mean plasma luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels among groups (P>). Daily spermatid production per gram of testicular parenchyma (DSP/gm) in Group 5 was lower than in controls (P<), whereas DSP/gm was not different among groups 1 to 4 (P>). There were no differences among groups (P>) in the percentage of Stage 8 tubules or relative number of Leydig cells. The mean diameter of Leydig cells was less for Group 5 than for controls (P<), but was not different for Groups 1 to 3 (P>).