fT3 is the only active hormone. T4 is simply a reservoir for fT4–>fT3. There is no receptor for T4
You are better off checking your oral body temperature when you wake up and mid-afternoon to eval thyroid function status. See below re temperatures.
Fast acting T3 makes fT3 labs sort of sketchy. In USA time release T3 is a compounding pharmacy only medication. I take 25mcg per day.
If one has elevated rT3, that blocks some fT3 action and with ample fT3 body temperatures can be low. In that case, taking T4 simply increases fT4–>rT3. Thyroid is more complex than TRT. If TRT hormones are perfect, one can have most of the same symptoms of low-T if thyroid function is poor. Thyroid lab normals are mostly useless, one has to seek optimal. fT3 should be mid-range or a bit higher.
Please read the stickies found here: About the T Replacement Category - #2 by KSman
- advice for new guys - need more info about you
- things that damage your hormones
- protocol for injections
- finding a TRT doc
Evaluate your overall thyroid function by checking oral body temperatures as per the thyroid basics sticky. Thyroid hormone fT3 is what gets the job done and it regulates mitochondrial activity, the source of ATP which is the universal currency of cellular energy. This is part of the body’s temperature control loop. This can get messed up if you are iodine deficient. In many countries, you need to be using iodized salt. Other countries add iodine to dairy or bread.
KSman is simply a regular member on this site. Nothing more other than highly active.
I can be a bit abrupt in my replies and recommendations. I have a lot of ground to cover as this forum has become much more active in the last two years. I can’t follow threads that go deep over time. You need to respond to all of my points and requests as soon as possible before you fall off of my radar. The worse problems are guys who ignore issues re thyroid, body temperatures, history of iodized salt. Please do not piss people off saying that lab results are normal, we need lab number and ranges.
The value that you get out of this process and forum depends on your effort and performance. The bulk of your learning is reading/studying the suggested stickies.