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Did you know that desiccated thyroid is stronger than artificial thyroid (liothyronine and levothyroxine)? And what's more, no-one knows why.

Say you're taking Thyro-Gold, which contains 50 mcg of T4 and 12.5 mcg of T3, and you want to switch to liothyronine and levothyroxine. You would think you would take 50 mcg of levothyroxine and 12.5 mcg of liothyronine, same as the Thyro-Gold. But no. The correct dosage would, in fact, be 37 mcg of levothyroxine and 9 mcg of liothyronine.

Why? Well, desiccated thyroid has 'hidden power' that makes it more potent than artificial T3 and T4.

In fact, the T3 and T4 in desiccated thyroid is roughly 35% more potent than artificial T3 and T4.

No one knows why, but it might be because of the T1 and T2 in desiccated thyroid.

Here's a passage from The Complete Idiot's Guide To Thyroid Disease which explains it well:

You should be aware that 2 + 2 = 5 when it comes to desiccated thyroid. For example, a 65 mg (1 grain) pill of Nature-Throid contains 38 mcg of T4 and 9 mcg of T3. Given that T3 is about four times as potent as T4, that works out to 74 mcg (38 mcg + 36 mcg) of T4. However, the Conversion Guide shows that a 65 mg pill of Nature-Throid is equivalent to a 100 mcg pill of T4. This fact comes from doctors who have decades of experience with patients switching between thyroid medications, and you'll find the same information in virtually any other conversion guide (for example, the RLC Labs guide at GetRealThyroid.com/conversion-guide.html).

You might reasonably ask where the extra 26 mcg is coming from. The truth is no one really knows. However, experts suspect that the T2 and T1 in desiccated thyroid account for its "hidden" extra power.

It's important to be aware of this discrepancy between desiccated thyroid's stated active ingredients and its actual potency. If your doctor isn't experienced with desiccated thyroid, he might look at only the active ingredients and prescribe too much for you. You should therefore always refer to the Conversion Guide when switching between medications.

So whenever you convert between desiccated thyroid and liothyronine, or between desiccated thyroid and levothyroxine, you have to take desiccated thyroid's hidden power into account, otherwise you might end up over or under-dosing.

Don't worry though. To make conversions easy, I've made have a dosage converter that takes desiccated thyroid's hidden power into account.