Not the study you are asking for but this is the one many refer to when they say ”500mg first cycle”.
Testosterone dose-response relationships in healthy young men - PubMed
Testosterone increases muscle mass and strength and regulates other physiological processes, but we do not know whether testosterone effects are dose dependent and whether dose requirements for maintaining various androgen-dependent processes are similar. To determine the effects of graded doses...pubmed.ncbi.nlm.nih.gov
600mg clearly builds more than 300mg but I think its not a linear curve going on forever.
Thanks for posting. This wasn't the study I was referring to, but it basically shows the same thing.
The biggest takeaway I remember from the other study was that 200-300mg seems to be the sweet spot where you get the most out of your dosage, while keeping side effects down.
LBM gains:
125mg/wk - 3.4kg
300mg/wk - 5.2kg
600mg/wk - 7.9kg
One thing to remember is that as test dosage goes up, the body holds more LBM in the form of water. So that makes the results even more in favor for lower doses... the small difference when doubling from 300mg to 600mg could be in large part due to water weight.