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T3 & T4 info
The T3 Story
T what?
Let's hear you pronounce it: triiodothyronine. There, now you know why the name is usually shortened to T3. T4 (thyroxine) and T3 are the main thyroid hormones. T3 is five to eight times as strong as T4 (taking into consideration that it's absorbed at a higher rate than T4), and it's biologically more active. T4 is like the food in your refrigerator, while T3 is like the food on your plate.
T4 is slow acting, with a half-life of about one week — after a week, you have about half the level of the T4 still in your body, a week or so later you have half of that half remaining, and so on. Its full effects aren't reached until about six weeks after starting or changing a dose, which is why lab tests are optimally done every six weeks or so until a patient with hypothyroidism has reached satisfactory and stable thyroid hormone levels. T3, on the other hand, has a half-life of about a day. People on T3 sometimes feel its effects within minutes after taking it.
T3 is available as a separate synthetic medication with the brand name Cytomel in the US and Canada, and Tertroxin in the UK. It's usually prescribed along with a synthetic T4 medication. In the US, a synthetic T4/T3 combination is available with the brand name Thyrolar.
Natural, desiccated thyroid from pigs' thyroids with the brand name Armour is sold in the US, and in Canada, desiccated thyroid with the brand name Thyroid is made by Pfizer (formerly by Parke-Davis). Westhroid and Nature-throid are available in the US, and Nature-throid is also available in Europe.
T3 or not T3
A thyroid gland that functions normally produces T4 and T3. Twenty percent of the T3 circulating in the body comes directly from the thyroid gland, and the remaining 80 percent comes from conversion of T4. Because of this conversion process, most doctors prescribe only synthetic T4 medication (Synthroid, Levoxyl, Levothroid, Eltroxin, Unithroid, and others). Many patients with hypothyroidism do fine on T4 only.
However, many others don't, and they need T3 supplementation in addition to T4. If the thyroid gland is malfunctioning and not producing enough — or any — T4, why assume that it still puts out enough T3, or that the body converts enough of its T4 to T3?
The addition of T3 often helps with many symptoms of hypothyroidism that may not disappear with supplemental T4 only. It has improved people's libido, memories, and vision. It has eliminated or greatly reduced brain fog, feeling cold, constipation, depression, chronic fatigue, headaches, insomnia, muscle and joint pain, and chronic sinus infections. For some people, but not all, it has helped them finally lose weight. A small percentage of people who try it feel worse or no better on it.
T3 tests
Do lab tests show if a person needs T3 supplementation? Sometimes. If free T3 is lower in its range than free T4 is, this suggests that more T3 would be beneficial for that person. On the other hand, some people who have posted in alt.support.thyroid have had lab results that did not indicate a problem with T3, but they still had symptoms of hypothyroidism, and the addition of T3 helped them.
Lab results do not tell the whole story. However, most people with hypothyroidism in alt.support.thyroid feel best when their free T4 and free T3 levels are in the upper part of their ranges. The exception is with people who are on desiccated thyroid. Because it contains a higher ratio of T3 to T4 than our thyroids produce, people taking it have a free T4 level that's lower in its range when the free T3 level is where it should be, in the upper part of its range.
Tell my doctor
Doctors are taught in medical school that T4 is the only thyroid medication that patients with hypothyroidism need. For many patients, that's true. The problem is that many other patients are left with reduced quality of life on T4 only — but their health improves greatly once T3 is added.
The medical establishment is increasingly looking at T3 in addition to T4 as essential treatment for some hypothyroid patients. Not having been educated on its use, however, some doctors are hesitant to prescribe it. That's why we've compiled references from medical journals and other sources that discuss the effectiveness, safety, and necessity of T3 supplementation for many patients with hypothyroidism.
The following are some ways to find a doctor who prescribes T3 for some patients:
Ask pharmacists in your area for the names of doctors who prescribe T3 (Cytomel or Tertroxin, depending on your country).
Search for a doctor on Mary Shomon's Top Docs list.
Ask in alt.support.thyroid or the thyroid.about.com forum if anyone knows of a suitable doctor in your area.
If your country or continent is listed on the Country Specific page, see if any of the sites linked to from that page have information about doctors and T3.
Bring medical references if necessary (see the column at the right) and ask your current doctor to prescribe at least a trial amount of T3.
Tell me more
See the links at the right on this and all the pages in the T3 section of this site. The T3 References page provides an overview of the references and why we need them. The compilations of references are divided into medical journal references and references from other sources, and each has a printer-friendly version so that you can take these references to your doctor if they're relevant to your situation.
The above list of symptoms that T3 has helped with is from the "T3: Patients' Experiences" compilations.
If you want to discuss T3 supplementation with your doctor, we recommend that you read through the files here, and perhaps print copies of them for your doctor. Because T3 is so much stronger and faster acting than T4, it's important to get the doses right. On pages 285 and 286 of his book The Thyroid Solution, Dr. Ridha Arem describes how to adjust T4 doses when supplementing T4 with T3. Some people in our group have brought this book to their doctors, and their doctors have used this protocol to successfully add T3 to the medication mix.
Kevin G. Rhoads discusses TSH, T3, and T4 in more detail in his Thyroid 101 and Basic Fallacies post. See also the related articles The Desiccated Thyroid Story and The TSH Story as well as Hypothyroidism Medication and Hypothyroidism Medication Comparison
T3 & T4 info
The T3 Story
T what?
Let's hear you pronounce it: triiodothyronine. There, now you know why the name is usually shortened to T3. T4 (thyroxine) and T3 are the main thyroid hormones. T3 is five to eight times as strong as T4 (taking into consideration that it's absorbed at a higher rate than T4), and it's biologically more active. T4 is like the food in your refrigerator, while T3 is like the food on your plate.
T4 is slow acting, with a half-life of about one week — after a week, you have about half the level of the T4 still in your body, a week or so later you have half of that half remaining, and so on. Its full effects aren't reached until about six weeks after starting or changing a dose, which is why lab tests are optimally done every six weeks or so until a patient with hypothyroidism has reached satisfactory and stable thyroid hormone levels. T3, on the other hand, has a half-life of about a day. People on T3 sometimes feel its effects within minutes after taking it.
T3 is available as a separate synthetic medication with the brand name Cytomel in the US and Canada, and Tertroxin in the UK. It's usually prescribed along with a synthetic T4 medication. In the US, a synthetic T4/T3 combination is available with the brand name Thyrolar.
Natural, desiccated thyroid from pigs' thyroids with the brand name Armour is sold in the US, and in Canada, desiccated thyroid with the brand name Thyroid is made by Pfizer (formerly by Parke-Davis). Westhroid and Nature-throid are available in the US, and Nature-throid is also available in Europe.
T3 or not T3
A thyroid gland that functions normally produces T4 and T3. Twenty percent of the T3 circulating in the body comes directly from the thyroid gland, and the remaining 80 percent comes from conversion of T4. Because of this conversion process, most doctors prescribe only synthetic T4 medication (Synthroid, Levoxyl, Levothroid, Eltroxin, Unithroid, and others). Many patients with hypothyroidism do fine on T4 only.
However, many others don't, and they need T3 supplementation in addition to T4. If the thyroid gland is malfunctioning and not producing enough — or any — T4, why assume that it still puts out enough T3, or that the body converts enough of its T4 to T3?
The addition of T3 often helps with many symptoms of hypothyroidism that may not disappear with supplemental T4 only. It has improved people's libido, memories, and vision. It has eliminated or greatly reduced brain fog, feeling cold, constipation, depression, chronic fatigue, headaches, insomnia, muscle and joint pain, and chronic sinus infections. For some people, but not all, it has helped them finally lose weight. A small percentage of people who try it feel worse or no better on it.
T3 tests
Do lab tests show if a person needs T3 supplementation? Sometimes. If free T3 is lower in its range than free T4 is, this suggests that more T3 would be beneficial for that person. On the other hand, some people who have posted in alt.support.thyroid have had lab results that did not indicate a problem with T3, but they still had symptoms of hypothyroidism, and the addition of T3 helped them.
Lab results do not tell the whole story. However, most people with hypothyroidism in alt.support.thyroid feel best when their free T4 and free T3 levels are in the upper part of their ranges. The exception is with people who are on desiccated thyroid. Because it contains a higher ratio of T3 to T4 than our thyroids produce, people taking it have a free T4 level that's lower in its range when the free T3 level is where it should be, in the upper part of its range.
Tell my doctor
Doctors are taught in medical school that T4 is the only thyroid medication that patients with hypothyroidism need. For many patients, that's true. The problem is that many other patients are left with reduced quality of life on T4 only — but their health improves greatly once T3 is added.
The medical establishment is increasingly looking at T3 in addition to T4 as essential treatment for some hypothyroid patients. Not having been educated on its use, however, some doctors are hesitant to prescribe it. That's why we've compiled references from medical journals and other sources that discuss the effectiveness, safety, and necessity of T3 supplementation for many patients with hypothyroidism.
The following are some ways to find a doctor who prescribes T3 for some patients:
Ask pharmacists in your area for the names of doctors who prescribe T3 (Cytomel or Tertroxin, depending on your country).
Search for a doctor on Mary Shomon's Top Docs list.
Ask in alt.support.thyroid or the thyroid.about.com forum if anyone knows of a suitable doctor in your area.
If your country or continent is listed on the Country Specific page, see if any of the sites linked to from that page have information about doctors and T3.
Bring medical references if necessary (see the column at the right) and ask your current doctor to prescribe at least a trial amount of T3.
Tell me more
See the links at the right on this and all the pages in the T3 section of this site. The T3 References page provides an overview of the references and why we need them. The compilations of references are divided into medical journal references and references from other sources, and each has a printer-friendly version so that you can take these references to your doctor if they're relevant to your situation.
The above list of symptoms that T3 has helped with is from the "T3: Patients' Experiences" compilations.
If you want to discuss T3 supplementation with your doctor, we recommend that you read through the files here, and perhaps print copies of them for your doctor. Because T3 is so much stronger and faster acting than T4, it's important to get the doses right. On pages 285 and 286 of his book The Thyroid Solution, Dr. Ridha Arem describes how to adjust T4 doses when supplementing T4 with T3. Some people in our group have brought this book to their doctors, and their doctors have used this protocol to successfully add T3 to the medication mix.
Kevin G. Rhoads discusses TSH, T3, and T4 in more detail in his Thyroid 101 and Basic Fallacies post. See also the related articles The Desiccated Thyroid Story and The TSH Story as well as Hypothyroidism Medication and Hypothyroidism Medication Comparison
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