Hey bro, good question. High doses of Gh, more than 5iu, can possibly speed conversion from T4 to T3. This would leave you with high T3, active thyroid hormone and low T4, inactive. Still, low T4 can leave you feeling hypo-thyroid. If you suspect that you have low T4, you should go to your doctor and find out. I wouldn't just start taking T4, assuming that T4 is low. Reason being, too much thyroid hormone may effect gains