Titration was mainly determined (sorry to disappoint) by the rate of PO (progressive overload) + side effects and continuous/non-lab health markers, such as HRV, RHR, BG and the like and also occasional lab blood testing, including HbA1c, organ health, etc… basic/general comprehensive panel to make sure there wasn’t any severe risk to health.
However, IGF-1 testing was rarer due to cost-cutting because I thought my subjective assessment of exogenous HGH effects based on progression, sides and general health markers was sufficient.
Regarding the point where most males saturated around 0.1 iu/kg, and after that point, the change was simply more side effects (which doesn't fit my side effect changes/profile completely), with minimal additional IGF-1 elevation, and the PO I observed after this proposed saturation point, I think we should consider:
1. other growth mechanisms from exogenous HGH dose increases were responsible for additional PO
1.1. non-IGF-1 mediated growth pathways cause significant PO/anabolism
1.2. alternative signalling cascades, direct receptor activation, enhanced satellite cell activation, improved nutrition partitioning, etc..
2. local IGF-1 production (in muscle tissue) was stimulated by increased HGH doses and this may have a saturation point higher than serum IGF-1 / local increases supported growth despite plateaus in systemic IGF-1
3. some other factor which coincided with increased HGH dosing was responsible for increased PO and this is a coincidence / additional HGH was largely wasted (even beyond the expected diminishing returns)
Conclusion: more funding needed (LOL) to repeat (but not to the same extreme extent) up-titration with exogenous HGH with more IGF-1 monitoring, as well as what
@Ghoul said about immunogenicity testing.