How much free T3 versus free T4 does the normal human thyroid gland produce? What is the ratio of natural production of T4 vs T3?

[rjb112]

What is the ratio of natural production of T4 vs T3 by the normal human thyroid gland?

I have heard figures such as 5:1, 10:1, and 13 to 16:1 T4 versus T3.

Please link any articles that go into this.

Thank you very much!

[helvella Administrator Thyroid UK]

diogenes has posted about this and is well-qualified to answer.

[rjb112 in reply to helvella]

Thank you very much.

[Heloise in reply to rjb112]

This is from Ray Peat:

[Heloise]

This is from Ray Peat:

V. Therapy

Years ago it was reported that Armour thyroid, U.S.P., released T3 and T4, when digested, in a ratio of 1:3, and that people who used it had much higher ratios of T3 to T4 in their serum, than people who took only thyroxine. The argument was made that thyroxine was superior to thyroid U.S.P., without explaining the significance of the fact that healthy people who weren't taking any thyroid supplement had higher T3:T4 ratios than the people who took thyroxine, or that our own thyroid gland releases a high ratio of T3 to T4. The fact that the T3 is being used faster than T4, removing it from the blood more quickly than it enters from the thyroid gland itself, hasn't been discussed in the journals, possibly because it would support the view that a natural glandular balance was more appropriate to supplement than pure thyroxine.

The serum's high ratio of T4 to T3 is a pitifully poor argument to justify the use of thyroxine instead of a product that resembles the proportion of these substances secreted by a healthy thyroid gland, or maintained inside cells. About 30 years ago, when many people still thought of thyroxine as "the thryoid hormone," someone was making the argument that "the thyroid hormone" must work exclusively as an activator of genes, since most of the organ slices he tested didn't increase their oxygen consumption when it was added. In fact, the addition of thyroxine to brain slices suppressed their respiration by 6% during the experiment. Since most T3 is produced from T4 in the liver, not in the brain, I think that experiment had great significance, despite the ignorant interpretation of the author. An excess of thyroxine, in a tissue that doesn't convert it rapidly to T3, has an antithyroid action. (See Goumaz, et al, 1987.) This happens in many women who are given thyroxine; as their dose is increased, their symptoms get worse.

The brain concentrates T3 from the serum, and may have a concentration 6 times higher than the serum (Goumaz, et al., 1987), and it can achieve a higher concentration of T3 than T4. It takes up and concentrates T3, while tending to expel T4. Reverse T3 (rT3) doesn't have much ability to enter the brain, but increased T4 can cause it to be produced in the brain. These observations suggest to me that the blood's T3:T4 ratio would be very "brain favorable" if it approached more closely to the ratio formed in the thyroid gland, and secreted into the blood. Although most synthetic combination thyroid products now use a ratio of four T4 to one T3, many people feel that their memory and thinking are clearer when they take a ratio of about three to one. More active metabolism probably keeps the blood ratio of T3 to T4 relatively high, with the liver consuming T4 at about the same rate that T3 is used.

Since T3 has a short half life, it should be taken frequently. If the liver isn't producing a noticeable amount of T3, it is usually helpful to take a few micorgrams per hour. Since it restores respiration and metabolic efficiency very quickly, it isn't usually necessary to take it every hour or two, but until normal temperature and pulse have been achieved and stabilized, sometimes it's necessary to take it four or more times during the day. T4 acts by being changed to T3, so it tends to accumulate in the body, and on a given dose, usually reaches a steady concentration after about two weeks.

An effective way to use supplements is to take a combination T4-T3 dose, e.g., 40 mcg of T4 and 10 mcg of T3 once a day, and to use a few mcg of T3 at other times in the day. Keeping a 14-day chart of pulse rate and temperature allows you to see whether the dose is producing the desired response. If the figures aren't increasing at all after a few days, the dose can be increased, until a gradual daily increment can be seen, moving toward the goal at the rate of about 1/14 per day

[rjb112 in reply to Heloise]

Thanks very much.

I'm currently taking only T4 (Synthroid), 50 mcg.

TSH: 1.66 uIntUnt/mL (Reference range: 0.55-4.78)

FREE T-4: 1.1 ng/dl (Reference range: .67-1.52)

FREE

TRIIODOTHYRONINE: 2.4 pg/mL (Reference range: 2.3-4.2)

Any suggestions on how much T3 (liothyronine or Cytomel) and T4 (Synthroid) would be recommended for me, if I wanted to start taking T3?

Thanks!

[Heloise in reply to rjb112]

There is so much involved, it is hard to predict how much you are eventually going to need. We produce a lot more T4 and I think your 10:1 ratio is what I have read but I think that's only because our body can produce more than you actually use. A desiccated hormone has 36 T4 and 9 mcgs. T3 so that is quite different from ours but the process has many steps to get to the real issue which is getting enough FT3 to all your cells and the receptors have to be open to it. I'm having a problem with links but if you go to How Stuff Works, they have a nice succinct article about thyroid hormone.

If you have just been diagnosed the doctors take the easiest route and hope it works for you. That is Levothyroxine.

You need to build up a level of thyroid hormone by increasing your dose every few weeks. If T4 is working for you you should feel improvements and in a few months you may end up on a dose of 125 mcgs. or even more. You need to get your T4 and T3 in the upper part of the range for each and your TSH around 1.0. If you don't feel improvement and find that your T4 is much higher than T3 it means your liver is not able to convert the levo. This can be due to many factors. If you have been hypo very long your system has been failing in areas of nerves, muscles, digestion, even brain function. So you slowly have to recover and it takes a while. You may need to supplement and your D and B vitamins are very important. Digestive enzymes or HCl with meals helps break down nutrients.

Your adrenals may be overworked from being hypo so they may need support as well. Don't be discouraged though because you can certainly feel better.

[rjb112 in reply to Heloise]

"You need to build up a level of thyroid hormone by increasing your dose every few weeks. If T4 is working for you you should feel improvements and in a few months you may end up on a dose of 125 mcgs. or even more"

I've been hypothyroid for about 15-20 years.

I had been on 75 mcg Synthroid for several years, but 6 months ago my primary care physician lowered that to 50 mcg because my TSH was below the reference range. My T4 was in the reference range and they didn't test free T3 even though I asked them two or three times. Turns out the VA (Veteran's Administration) lab doesn't even test for free T3....they have to mail it out to Quest for that test.

This time I finally was successful in getting them to order free T3, so I can't compare my free T3 serum level with a past measurement.

[Heloise in reply to rjb112]

Sorry, rjb, I assumed you were new but now I'v looked at a few of your posts and see you have been hypo for almost as long as I. It is distressing that doctors are going by the TSH score. The Free T3 is a better evaluation but you can't trust even that completely. Goodness how much T3 will they allow? If this is going to be a struggle I urge you to try dosing yourself. I'm in NY state and can't even use mail order lab tests. It's totally ridiculous.

[rjb112 in reply to Heloise]

"It is distressing that doctors are going by the TSH score."

Yes, that's what my doctors seem to go by....they don't even order free T3 unless you hound them very persistently.....and as I mentioned, the VA doesn't even do a free T3 test....they had to mail it out to Quest Diagnostics lab.

For example, they lowered my Synthroid from 75 mcg to 50 mcg just because my TSH was below range, even though my free T4 was not above range or even at the top of the range.

I live in Los Angeles....and fortunately, I can go to a private lab to get blood tests, but now it looks like I can get whatever thyroid test I want at the VA since the VA is willing to send the blood out for a free T3 test.

"Goodness how much T3 will they allow? If this is going to be a struggle I urge you to try dosing yourself."

Yes, it is going to be a struggle.

Years ago I asked my primary care MD to put me on some T3 (liothyronine/Cytomel) along with my T4, and she said she couldn't do that and sent me to endocrinology. The endocrinology resident said she wouldn't put me on T3, "because T4 is converted to T3, blah blah blah"......

I could try to fight the battle again now as it's been some years.....but yes, it is going to be a struggle.

"I urge you to try dosing yourself".

How can I do that?

Is T3 available without a prescription?

I would like to start out with maybe 2.5 mcg of T3 daily, or I could start with 5 mcg T3 daily and cut my dose of Synthroid somewhat.

But where would I get the liothyronine/Cytomel?

And is it a reputable source, a reliable source?

Actually, I'd like to be transparent to my primary care MD about this......

I'll ask her to put me on some T3.....if she says she can't and sends me to endo, I'll ask them......

If they say no, I'll tell them, OK, I'm going to get the T3 on my own and take it......but I want you to continue doing the blood work to check the results.

I'd like to do it that way.

But I have no idea where to get T3, from a reputable source.

[Heloise in reply to rjb112]

Will you recognize a private message? It will be at "Chat".

[rjb112 in reply to Heloise]

I've never received one before.

Where do I go to find the Private Message?

What do you mean by, "It will be at "Chat" ?

Where is "Chat"?

[helvella Administrator Thyroid UK in reply to rjb112]

Here is the Help topic on Private Messages:

support.healthunlocked.com/...

[Heloise in reply to Heloise]

It's left of the bell....up in the header.

[kiefer in reply to rjb112]

They will probably refuse to treat you if you tell them you'll obtain thyroid medication on your own. I said the same thing to a little nurse practitioner and she was totally unwilling to continue to treat me because it still increased her liability. She explained there was a mandate placed on not only her but of all doctors and that was, the TSH rule. She wouldn't go below the normal range or she'd face consequences from the board of medicine, should they discover the misdeed.

Keep in mind that If you do add T3 to your dosing regimen, there's a possibility that your TSH will become suppressed. For some of us, it doesn't take much. I went from:

1 grain of desiccated thyroid (38mcg/9mcg T4/T3) TSH: 1.38 to

1.5 grains (57mcg/13.5mcg) TSH: 0.03.

As I was being "fired", the little NP screamed at me, "You were hyperthyroid!!!!" except that... there were no symptoms except hypothyroid ones.

Should you decide to self-treat, obtain your entire replacement dose because you'll not be able to meet their minimum TSH level requirement, unless you buy some thyroid stimulating hormone online, and inject yourself (not recommended) just to get your levels back into the normal range.

The doctor won't care what you're doing....they'll drop your dose to get your TSH level back in the normal range. End of discussion. Whew! no more liability for him, he's thinking.

What made me come to the conclusion that this behavior was primarily fear-induced was the fact that doctors actually have a lot of authority to experiment. They can prescribe drugs for unlabeled uses, like trazodone, an antidepressant, for insomnia. I suppose they could even pull some leeches out of a drawer and try that again. But when it comes to the treatment of hypothyroidism, there is a perfect storm of ignorance, fear of liability and the desire to go along just to get along.

From a doctor's perspective, hypothyroidism, if they don't have it, is apparently a boring disease. Just ask any endocrinologist. I think one of the reasons they're so rude to their hypothyroid patients is that they feel insulted. Hypothyroidism, to them, is no more complex than changing someone's bandage. Anybody can prescribe thyroid hormones. But how many doctors can treat thyroid cancer? Now you've got the endocrinologist's attention. The yawning stops.

I found that negotiating was a critical skill set in addition to understanding thyroid physiology, disease, diagnosis and treatment. Most doctors are thyroid ignorant but some of them are open-minded. Every one of them, though, remembers when doctors were being sued by their patients like it was a new fad. So doctors go out of their way to protect themselves from a histrionic patient who calls the board of medicine and complains. If it's thyroid-related, that doctor is screwed because they are, in writing, very strongly discouraged from using drugs other than levothyroxine. And if they go outside the TSH range, which often is required, they'll get no support from endocrinologists, who will most likely refuse any of their referrals, because that doctor has gone "rogue". So there is enforcement from within and from the boards of medicine.

When faced with the usual "No" regarding a thyroid drug or dosage change, some questions that everyone should consider asking their doctor are these:

"Is there something you're afraid might happen if I were to take this higher dose/ other drug (T3)? How would it affect you?"

"Are you concerned about your liability if the TSH is lower than the normal range?"

"Have you had any patients who have died from thyroid medication overdose? Then what's the harm in an increase?"

"These drugs are considered safe and effective, right? So why the hesitation?"

"What documentation (vital signs, etc.) could I provide you with so that you'd trust me to protect your liability?"

"I know you have the authority to prescribe and be flexible with thyroid hormone dosages...what if this is the key to getting my health back?"

"Can't we just rule it out (argument against "It's not your thyroid.")? What harm would come to 'either' of us if I were given a trial dose for a few months?"

"You say you can't increase the dose because my TSH is too low. But isn't the actual thyroid hormone T3 that regulates my metabolism? If my Free T3 level isn't above the normal range, wouldn't that suggest that I'm not hyperthyroid?"

"Don't you think I would tell you if I had symptoms of overstimulation? Nobody would continue taking a dose that causes a pounding heart, diarrhea, anxiety, insomnia..."

"An insulin diabetic monitors their own dose. Don't you think a thyroid patient would recognize adverse symptoms and act appropriately?"

"Is this a trust issue? Do you not trust me to watch out for both yours and my health interests?"

"If I bring you an actual medical journal article explaining why the TSH test is not good for dosing, will you read it and reconsider your position?" (have this ready so you can pull it out right then and show the doctor)

I challenge anyone to ask those questions to their doctor. The answers might just surprise them. I would guess that nobody has ever done it. I decided that it was worth the risk and began negotiating:

When I told my last doctor that I "had his back" regarding his liability (because I was documenting my vital signs and I would give him paper reports every time I saw him) he broke out into a big smile and he looked both delighted and relieved. I got him to go way beyond his comfort zone (for a while) because he knew I was, as they say in sales, "addressing his real objections."

[rjb112 in reply to kiefer]

"If I bring you an actual medical journal article explaining why the TSH test is not good for dosing, will you read it and reconsider your position?" (have this ready so you can pull it out right then and show the doctor)"

kiefer, can you like a few articles that you think are the best? I'd like to read them myself!

Why do doctors go by the TSH rather then by free T3?

"Don't you think I would tell you if I had symptoms of overstimulation? Nobody would continue taking a dose that causes a pounding heart, diarrhea, anxiety, insomnia..."

that's right on the money, because I once had a too high dose of thyroid hormone, and it was very uncomfortable being hyper. I had a very difficult time waiting in line in the supermarket....feeling hyper due to too much thyroid hormone is very uncomfortable and unpleasant.

[kiefer in reply to rjb112]

How Accurate is TSH testing?

nahypothyroidism.org/how-ac...

There are a number of reasons why doctors go by the TSH test, rather than by the Free T3.

1) The TSH test was touted as the most accurate indicator of tissuel level T3. This marketing myth was so appealing to doctors and they wanted so badly to believe it that it was adopted and they refuse to let it die. Since that time, doctors have published articles touting the accuracy of the TSH and why it can be used as the sole test in diagnosis AND dosing.

ncbi.nlm.nih.gov/pmc/articl...

2)During the "Gold Rush" of thyroid testing, many of the tests for free T3, Free T4, etc. were found to be unreliable, due to flawed testing procedures. As a result, all of them were abandoned, except for the TSH test. While today's FT3 and FT4 tests are much more reliable, many doctors only remember when they were crappy and refuse to use them again.

3) The Free T3 may not be accurate as an indicator of hypothyroidism...

According to Dr. John C. Lowe, author of "The Metabolic Treatment of Fibromyalgia", page 802:

"The free T3 test is most useful as an indicator of hyperthyroidism. Mardell and Gamlen wrote that the upper limit of the free T3 is of use in identifying patients with thyroid gland overactivity or an excess dosage of exogenous thyroxine. They also wrote that the significance of the high free T3 to the patient's thyroid status should be assessed by the use of a supersensitive TSH assay. They noted that the lower limit of the free T3 is an insensitive indicator of hypothyroidism and is of little value in diagnosing this condition. This concurs with the reports of other writers. Hamburger stated that the free T3 is as useless as the total T3 assay for diagnosing hypothyroidism."

[Heloise in reply to rjb112]

Since T3 is much more potent people will start with 5 mcgs. or less. A common dose for many people is two grains of an NDT, OR 125 mcgs. of Synthroid OR a combination. I am taking only T3 and take 50 mcgs. but people can take more or less of any of these. Instead of increasing Synthroid you could add some T3 as a combination of T4 plus T3 is a sensible method of treatment. It should be done gradually so your body can acclimate. You can also take your temperature and see if it improves.