I find there is much less muscle loss with T4, plus I'm on tren which lowers thyroid output so it's a good idea to add T4. T4 makes HGH use more anabolic as well. The process of allowing the body to convert T4 to T3 aids in making HGH more anabolic.
t4 is a must with hgh.HGH suppresses your thyroid and your T3 output.