I'm confused by this last statement. My understanding is synthetic exogenous T4(synthroid) converts to T3 once ingested, they both are prescribed for hypothyroidism and have the same net effect but T3 is not often prescribed because it's considered too strong with a high peak saturation since it doesn't have to convert, which cause unstable levels. T4 is used more because it has a longer more stable effect while the body will slowly convert it to T3. So how will T4 increase the anabolic effect of gh but T3 lower it??
Thanks for the info guys.
Apologies for the essay bro. Your statement is accurate unless exogenous GH is used. GH increases the conversion of T4 into T3. The conversion process of T4 to T3 by the D1 and D2 enzymes is critical for GH to exert its anabolic and nitrogen-retaining effects on muscle, which won't occur if T3 levels are highly elevated due to its effects on the negative feedback loop sending a signal to the thyroid axis to cease the release of the D1, D2 enzyme and release the D3 enzyme. The D3 enzyme halts the conversion process of T4 and T3.
In the past, exogenous T3 was considered by some to be the answer to GH use since they are both synergistic and are, but that is with the D1, D2 enzyme. The issue is with exogenous GH use, those enzymes are inhibited, and the inhibitor is the D3 enzyme.
It all comes down to those 2 enzymes needed for conversion as the conversion process is what increases the anabolic effects of GH. There was a study done on people with lacking natural growth hormone, and it was clear GH needed elevated T3 levels to exert its effects but through study all this was done with the use of T4 to create more conversion. You can't continue to maintain high T3 levels with low T4 levels cause the body won't allow it via the D3 enzyme.
When I first started studying this a few years back, it was confusing, and there are a lot more in-depth reasons like GnRH, IGF, GH, and a lot of receptor effects, etc. It's not an easy study to grasp, but I will say in real-world experience, I see GH + T4 have more profound effects on muscle than no T4 or GH + T3.