Maybe this can help you:
INSULIN AND THYROID HORMONES
With the huge increases in fat mass often accompanying insulin use, it seems like a simple solution to use thyroid hormone. Unfortunately, this doesn't work out very well. The reason is that thyroid hormone (specifically T3 and possibly T4) increases the amount of the "bad" IGF1-BP's mentioned earlier;IGFBP2 and IGFBP4. This may not seem like a big deal if one is not using drugs to stimulate IGF-1 synthesis, but IGF-1 levels are naturally stimulated through acts like stretching, and even natural testosterone/GH increases. All of these things normally accompany workouts (if you know what you're doing), which is the best time to take insulin. So by having all of the free IGF-1 bound by IGFBP3s' evil siblings, much of the anabolic effect of insulin is lost! Since T3 (triiodothyronine) is the main culprit, does that mean that T4 (tetraiodothyronine) can be used with no detrimental effect? NO, because T4 is mostly effective by converting to T3, which leaves you with the same problem. In fact, T4 could very well do the same thing. So if you want to maximize the anabolic effectiveness of insulin while minimizing bodyfat accumulation, use another fat burner and leave the thyroid alone.
