There are two well known synthetic thyroid hormones commonly administered by bodybuilders known as T-4 and T-3. (*See "Synthroid" and "Cytomel" for more info) However, some have not yet heard of another natural thyroid hormone called T-2 or Ldiiodothyronine.
The good new is that it is highly active and naturally occurring in some foods such as beef products. It is also non-prescription in many countries…so far. The bad news is that since it works quite well and offers individuals freedom of choice, it probably will not be legal for long.
So far, T-2 seems to be slightly more effective for fat oxidation (burning) than either T-4 or T-3 alone while offering an improved protein sparing-like result. This may be true. T-2 stimulates cellular mitochondria (cellular energy producers) more so than the cell nucleus. This means, unlike T-4 and T-3, T-2 is less likely to activate other cellular functions and more likely to focus upon increased metabolic rate or energy expenditure. Personal experience had shown an excellent synergistic effect between T-2, Norephedrine, and ephedrine plus caffeine. This is due to an interesting interplay between the substances.
1.T-2 increases resting metabolic rate by stimulating mitochondria expenditure of energy from calories. T-2 also increases Adenylate Cyclase production. Adenylate Cyclase is like a master enzyme in our bodies that positively effects most other fat burning and muscle building enzymes and hormones. As example, adenylate Cyclase elevation results in an increased rate of production of cyclic AMP (cAMP) from ATP. This forces fat cells to give their stores to be used as fuel for energy production. The result is an increase in fatty acid (fat) oxidation and a protein sparing effect because fat becomes favored muscle cell food.
2. Norephedrine and ephedrine mimic and stimulate the release of the adrenal hormones norepinephrine and epinephrine. Norephinephrine raises heart rate and epinephrine stimulates carbohydrate metabolism resulting in an increased metabolic rate, fatty acids release from lipocytes (fat cells), and a protein sparing effect. Caffeine simply prolongs the effect.
T-3 is about 5 times more active than T-4, and some research suggests T-2 is more active than T-3. My experience to date has been that this just is not the truth. But, T-2 does offer a reasonably safe non-prescription alternative to the use of synthetic T-4 or T-3 drugs in countries where it is still an OTC product. Of course some idiots somewhere will find a way to hurt themselves with it and show up on day time talk shows. Like the guy who discovered nail guns can inflict a law suit based injury if held to one head just so. (This really happened)
There is also the drug synergy that results from a T-4, T-3, T-2 stack to consider for overall effectiveness and reduced dosage requirements. Some athletes have reported an improved rate of fat loss and better lean tissue retention with this technique.
Most T-2 users reported an increase in metabolic rate and activity proportionate to dosages as listed. This supplement has been noted as exceptionally beneficial for individuals who have a slower metabolic rate naturally that results in above normal fat storage and poor post-training recovery at a dosage of 50 MG, 4 times daily. Others had found the higher listed dosages necessary for rapid fat loss at maximum rates. Most reported improved rate of recovery, improved lean mass to fat ratio, and often an increase in libido. (No Joke)
T-2 has a half-life of 4-6 hours. Due to this brief period of activity users reportedly divided dosages into 3-4 daily administrations to maintain constant circulating T-2 levels and the resulting metabolic rate increase.
T-2 use can create a negative feedback loop at higher dosages and due to prolonged use. The result was often metabolic lag usually for 3-7 days after discontinuance. (See guggulsterones and Coleus Forskohlii for common reported solutions)
Athletes also used T-2 post-AAS use as a means of avoiding post-cycle metabolic lag. (50 MG 4 times daily)
L. Rea (2002) - Chemical Muscle Enhancement Bodybuilders Desk Reference