You're correct, testosterone's negative effect on collagen production increases as the dose rises. "Normal" levels of testostrone don't reduce collagen production, but as soon as we start to go outside of a failry normal range, it begins to have this effect.
The following is a partial cut & paste from an article referencing 2 studies, which looked at the negative effects nandrolone had on the tendons:[/B]
There were some very interesting findings after seven weeks of training with anabolic steroids, compared with the natty (natural) group of rats. The natty group did not have any biochemical changes in the rat tendon/collagen properties, while the anabolic steroid group had major changes.(6) The Deca-Durabolin group had reduced biochemical properties of genes involving tendon and collagen strength.
It is interesting to note that AAS administration reduced the accumulation of IGF-1 mRNA levels in some tendon regions, compared to the non-treated, trained group. This decrease of IGF-1 mRNA levels induced by AAS administration may be related to the observed decreases collagen expression when considering the possible connection between IGF-1 and collagen synthesis.(8) The AAS treatment also decreased the MMP-2 mRNA expression (this gene encodes an enzyme for collagen).
The above study is similar to another recently published study, which showed that nandrolone impaired the healing of rotator cuffs of rabbits. In the latter study, male rabbits underwent an incision in the rotator cuff and were divided into groups with anabolic steroids (nandrolone decanoate, 10mg/kg) and natural recovery. Groups that did not receive anabolic steroids showed better healing and more tendon strength compared to groups that received anabolic steroids. Microscopic examination of specimens from the groups with anabolic steroid use showed focal fibroblastic reaction and inflammation, suggesting an impaired healing response.(7)