FT4 testing on treatment with medications containing T3

In the 'Recovering with T3' book I repeatedly say that thyroid blood tests cannot be used to manage T3 based thyroid treatment.

However, many thyroid patients often have problems with their family doctor or endocrinologist because of concerns about low FT4 levels.

One thyroid patient has recently brought some additional information to my attention. With each prescription medication comes a manufacturers insert - the piece of paper accompanying the medication for the pharmacist. This describes the medication, how to use it and any contra-indications. Sometimes, a pharmacist will retain the insert and sometimes the insert will be provided to the patient along with the medication. The information on this insert is based on clinical research and on tests approved by the FDA (US Food and Drug Administration). This information on the manufacturer's insert with a drug is usually not in question. These inserts are sometimes not available on the Internet but they come in the box with the medication.

This thyroid patient uses Cytomel, which is a common brand of synthetic T3. The actual manufacturer's insert for Cytomel does not appear to be available on the web. There are stripped down versions of it, purporting to be the insert  But she has the actual insert, so she knows it is more comprehensive.

On the Cytomel insert it states: "Serum T4 levels can be used to test the effectiveness of all thyroid medications except products containing liothronine sodium."

That is the manufacture stating, if it's got T3 in it, you can't rely on the tests for FT4. And in the US, the manufacturer states these things based on test run by the FDA.

So this isn't in question - FT4 cannot be used to test the effectiveness of medications containing T3, or at the very least the same rules as normal cannot be used if the doctor is attempting to review FT4.

The same manufacturer states doctors should be using laboratory tests in addition to "Full clinical evaluation", i.e, considering the patient's presenting and stated symptoms. The upshot being, the doctors failing to do a full clinical evaluation are the ones not using T3 medications as directed.

I thought this was fascinating as it is much closer to the position I take within the 'Recovering with T3' book. I see this information being particularly relevant to those thyroid patients using T3 medication or combining T3 medication with T4 or natural desiccated thyroid. Frequently, these people are asked by their doctors to reduce their T3 or add T4 because of FT4 levels that are lower than the doctor cares to see. This is clearly not a good approach, especially when the health of the thyroid patient is actually improving.

You can find the Cytomel manufacturer's insert here. The quality of the scanned document is not perfect but it is readable once it is magnified a little. For completeness, at the end of this blog post I also include the manufacturer's insert for a synthetic T4 product Tirosint by way of comparison to the T3 product for those that are interested.

If any thyroid patient has any other manufacturer insert for other T3 or T4 products then I'd appreciate good quality scanned images of these sent to the 'Contact Us' page of my website. I'll eventually put up a blog post with all the various inserts listed.  It is also worth noting that these are not static documents. The drug companies continue to update these inserts as new information comes to light via doctors, patients, and drug trials. The Cytomel was put on the market in 1954. But the Cytomel PDF document was last updated as of March 2004 (see the last line above the King logo).

If anyone is interested in T3 trials being run (now, in the past, or upcoming)  the US govt lists worldwide trials. Here is the site for T3 trials. This is interesting. It shows there is research going on, but none of it centered on helping average hypothyroid patients. Mostly depression and weight loss: http://www.clinicaltrials.gov/ct2/results?term=Liothyronine+Sodium&Searc...

Best wishes,