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Thyroid Hormones

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Berardi

T2 - The Fat Terminator?

Berardi JM
First published at www.thepowerstore.com, Sep 14 2001.

"Recently, Biotest Laboratories has released a very interesting product that they are calling T2 (otherwise known as 3,5-diiodo-l-thyronine or just diiodothyronine). T2 is definitely a legitimate thyroid hormone, structurally very like T3 or T4. However this product is allowed to be sold as an over the counter dietary supplement due to the fact that is present in meat.

In the past, T2 was thought to be inactive, but many recent papers have shown T2 to have some pretty dramatic effects on metabolic processes. One issue of concern in the interpretation of this data is the fact most of these studies used hypothyroid rats that are producing very little thyroid hormone on their own. Therefore since these studies did not examine the effects of adding T2 into a normal thyroidal environment, they may not be totally applicable to individuals with normal thyroid functioning. In any case, the studies are certainly worth mentioning.

• Significant increases in mitochondrial respiration and cytochrome oxidase activity were found both in vitro and in vivo (1). These increases lead to an increase in metabolic rate. Interestingly, these effects are different from those of T3 and T4 due to the fact that T2 acts directly on the mitochondrial respiration while T3 and T4 must first increase oxidative enzyme levels. This means that T2 has a much more rapid stimulation of metabolic rate (1 hour for T2 vs 24 hours for T3). Some authors have concluded that T2 may be beneficial in rapid energy requiring situations like cold exposure or overfeeding (2).
   

• Significant increases in resting metabolic rate (33%) were found (1,3). Both T2 and T3 were able to stimulate the recovery of metabolic rate to normal, euthyroid levels.
   

• Significant increases in the oxidative capacity of skeletal muscle, brown adipose tissue, liver, and the heart were found (1,4). Both T2 and T3 promoted full recovery of oxidative capacity but T2 was most active in the liver and the muscle while T3 was most active in the liver.
   

• Significant increases in the liver activities of glucose-6-phosphate dehydrogenase and malic enzyme were found (5,6). These enzymes are necessary for fat metabolism.

• Significant increases in GH release were found. Both T2 and T3 increased GH release 5-fold (7).
   

• In the one human study I found, T2 Significantly increased oxygen consumption in blood cells in vitro (8).

In most of the studies listed above, the doses of T2 required for physiological and biochemical effects to manifest were larger than the doses of T3 required. This is due to the fact that T2 has a lower receptor affinity for most thyroid hormone receptors than does T3.

So from these data, if the dose is right, T2 supplementation may offer most of the same benefits as T3 but might even be superior in rapidly stimulating metabolic rate.

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