
Originally Posted by
someguyfromanotherforums
Yes. Clen has a similar effect to ephedrine.
It's mode of action is through the Beta-2 adrenoreceptors. It's a selective Beta-2 agonist.
Stimulation of this receptor causes more T4 to be converted to T3 in your thyroid by the de-iodinase enzyme. (80% of your bodies cicrculating free plasma T3 is converted from T4). i.e. Free T3 in your body = T3 produced by your thyroid(20%) + The T3 converted from the T4 produced by your thyroid via the de-iodinase enzyme, which basically just cleaves off an iodine molecule(80%).
Now, after about 2 weeks of Clen ED( results will vary acording to dosage and physiology, but I would say 2 weeks at 100mcgs/day for a 180lb male will translate to 2 weeks plus/minus 2-3 days), your T4 (that's being producedby the thyroid) that's being converted to the metabolically active T3(Which is what is chiefly responsible for your increase in Metabolic rate, and which is being produced in quantities: 20% by your thyroid and 80% by the T4-T3 conversion I mentioned above) will start being converted to rT3 (reverse T3), the molecular mirror-image of T3 that's metabolically inert. At that moment Clen's stops working and your Plasma T3 levels drop, your rT3 levels go up, and your T4 levels stay about roughly the same. All this basically adds up to to a drop in your metabolic rate until your de-iodinase enzyme can basically re-charge itself back to normal levels, and start back up converting thyroid produced T4 to T3 again via the cleaving of an iodine molecule.
As mentioned, L-taurine ( A very cheap, colorless, and virtually tasteless amino acid. 300g goes for $10 or less) in the 6-10g range..in 2 split dosages AM and PM, can stop this T4-rT3 conversion for another one week or two through cell voluminization. However, in the end, you're eventually going to have to add synthetic T3 to overcome the rT3 problem. But that's a topic for another time because it would take a very long time to explain.