T
T4
T4 or thyroxine is the primary thyroid hormone produced by the thyroid gland. T4 is largely a prohormone (storage form). The body converts it into the more active T3 via deiodinase enzymes. T3 is the direct, potent driver of metabolic rate and fat burning. T4 works more indirectly and generally produces milder effects
Exogenous T4 (alone or more commonly stacked with T3) is typically researched during cutting phases to elevate metabolism and support fat loss. It is one of the thyroid hormones used for this purpose, though pure T3 (Cytomel/liothyronine) is generally preferred when the goal is aggressive, rapid fat loss because it does not rely on conversion.
T3:T4 combinations are researched together because the mix provides more stable thyroid support while still accelerating fat loss
Pure T4 only research is less common because conversion to T3 can become inefficient under the stress of a calorie deficit, training, and low body fat
Research application
Copied from the handbook as research notes. and not instructions.
Always treat any dosage information as what has been observed in research and not instructional
- Starting range: Often 25 - 50 mcg per day
- Typical working dose is often in the 50 -100 mcg per day range when used for fat-loss support
T3:T4 combinations: A common ratio is 1:2 (T3:T4). Some researchers describe peaks around 50 mcg T3 + 100 mcg T4 with advice not to exceed those levels
Dosages are usually kept relatively moderate compared with high-dose T3 protocols and cycles are often limited in duration, similar to T3 use
Unless other wise noted intermuscular (IM) peptides are commonly administered via subcutaneous (SQ) injection with 30-31 gauge syringes
From @BowTiedYukon