if you are running gh your thyroid is already being suppressed so for starters, that is why the addition of T3 and/or T4 is helpful. i am using t4 now and it is working better than the T3 but i am not 100% sure that is becuase it is T4 or because my T4 is human grade (whereas my T3 is research chemical). the best dosage seems between 100-200mcg. in general i think it is safe to stay on it as long as your gh run goes, but i would taper it at the end.