I've read some about T3, and have come across the same claim on different boards about how T3 doses at 12.5 mcg per day will increase muscle protein synthesis while on cycle. My question(s) is, even if there is any truth to this claim, isn't 12.5 mcg lower than what a healthy adult thyroid will output (25mcg approximately)? Wouldn't this slow the thyroid down because it is less than one's own endogenous production? Or is there an additive effect, in other words, it works alongside your endogenous production?
I use T3 regularly in my cycles for MPS purposes. Most guys I know who use T3 for this purpose run 25-50 mcg. Per their feedback, I know 25 mcg works well. However, I only have experience running 50 mcg (which also works well) because I've never cared to break up my little pills up.
Your natural T3 production will be effected at these doses, which may mean production slows down or stops. This is dose and duration dependent. One unorthodox but effective method to minimize this effect (and aid faster recover) is to not run T3 every day. I've ran 2 different protocols: 2 on, 1 off and 5 on, 2 off. These methods keep your thyroid from adapting. I prefer the 5 on, 2 off because this fits my schedule better because I usually workout 4-5 days during the week and take the weekends off.
Every time I've ran one of the protocols above, recovery has been fast and easy. Once I tried the traditional ED protocol and recovery was much slower and I felt like 'death' for about a week. I also recommend Now's Thyroid Energy supplement as a T3 PCT.
One more thing that you won't hear or read about...
Try overlapping or staggering your T3 with your AAS or other stims. Meaning, end your T3 run with 2-4 weeks left on your AAS cycle. This allows you to recover in a 'super' state with elevated androgens. Never stop your AAS, T3, Stims, etc. all at the same time.