Definitely something that will become a rate limiting factor at the high end/duration of consistent HGH usage. For some people that will take longer than others. Of course bloodwork is the only real way to know if it's something worth pursuing. I would never categorically suggest anyone just start popping thyroid medication only because they are taking HGH.
BINGO!! Thank you kits4less for hammering that home about not simply taking something just because....to many guys get caught in that trap it's like taking Adex with every cycle. Why would you do that unless your labs tell you too?? .....This is a very well written article from Anthony Roberts from 2006 explaining the function of T4 and T3 while using GH it's a good read