This archived forum used to be called 'Peatarian' (in reference to Ray Peat).

T2: The Forgotten Thyroid Hormone

-3,5-diiodo-L-thyronine increases resting metabolic rate and reduces body weight without undesirable side effects.

-3,5-diiodothyronine (T2) has been shown to powerfully reduce adiposity and dyslipidaemia and to reverse hepatic steatosis without unfavourable side-effects usually observed when T3 or T4 is used.

-T2 increased state 4 and state 3 oxygen consumption and raised ATP synthesis and hydrolysis, which were reduced in hypothyroid rats.

-Stained sections showed that T2 treatment reduced hepatic fatty accumulation induced by a high-fat diet. ... Moreover, by stimulating mitochondrial uncoupling, T2 caused less efficient utilization of fatty acid substrates and ameliorated mitochondrial oxidative stress.

-These results indicate that T2s and T3 exert different effects on RM. The effects of T2s are rapid and possibly mediated by their direct interaction with mitochondria. Those of T3 are slower and more prolonged, and at least partly attributable to a modulation of the cellularity of tissues that are metabolically very active."

There is more about T2 on this link. Overall, it seems as if T2 has some very profound metabolic effects independent of the action of T3. The typical argument is something like: "But T2 is simply T3 with one less iodine atom. It will just get converted inside the body from T3." Well, yes, in theory. But also in theory, T3 should have no problems converting from T4. You can ask all those people on synthroid (and other T4-only replacements) how well that works for them. There are various types of stress (such as chronic dieting, exercise, diabetes, etc.) which inhibit the activity of the deiodinases required for conversion of T4 to the other hormones.

This would make the case for using whole thyroid glands, or whole thyroid extracts as opposed to just T4 and T3, much more appealing as they typically contain T4, T3, T2, T1 (monoiodothyronine - still have to research this one) and calcitonin, all hormones which are biologically active in one way or another but the body may have trouble converting from the higher forms.

Sadly it seems these days people don't have much success with extracts like Armour, perhaps due to the new binders such as cellulose which significantly reduce the activity of the hormones inside. Thus, potentially, a better formulated thyroid extract would prove their superiority.

asked Mar 12, 2013 by JuiceUser
Great post and great info. Thank you !

1 Answer

I asked Ray about T2. Here's our short exchange:

Very curious to hear your thoughts on the use of synthetic T2 therapeutically. I have read that it can be even more effective at raising the metabolic rate than T3. It is also currently over-the-counter, though difficult to source. The products I've seen are 150mcg per capsule, which seems quite high to me. I've seen both 3,5 and 3,3'-Diiodo-L-Thyronine. Have you read or experienced if one is more effective than the other?

His response:

Mitochondria have the enzyme for converting T3 to T2. The potency seems crazy, the body needs only about 4 mcg per hour.

answered Mar 12, 2013 by wilson