Please would someone explain why some need to t... - Thyroid UK

Thyroid UK
109,924 members127,769 posts

Please would someone explain why some need to take T4 as well as T3?


I thought T4 needed to convert to T3 anyway for it to be any use. So why take T4 if you are taking T3?

10 Replies

You really don't need synthetic T4 but it is preferred by the medical profession as that's what replaced Natural Dessicated Thyroid Hormones, which contains, T4, T3, T2, T1 and calcitonin and maybe some other things of which we are unaware. T4 is cheap approx £1.50 per month, but if you include secondary medications for clinical symptoms which we are told are not due to the thyroid gland as our blood tests are 'in range' the cost is much higher per month, plus, for some, constant ill-health. T3 is very expensive (why I don't know). It is the active hormone which we need and the brain contains the most cells in our body and they need T3.

T3 is also stronger than T4, i.e. 20mcg T3 is equal to 100mcg T4 approx.

Everdean in reply to shaws

Thank you Shaws.

Everdean in reply to shaws

Just read this report you sent, but I still don't understand why they include T4. Surely it's not necessary if T3 is given.

shawsAdministrator in reply to Everdean

I think it is because the medical profession believe T4 is the preferable treatment for hypothyroidism prescribed by the Endocrinologists and GP's. Very few patients get T3 alone but some do get T3 added to a reduced T4. They don't believe their patients still feel unwell on T4 alone if their TSH is within range whereas many patients feel better when their TSH is very low or suppressed but cannot get some extra T4 prescribed.

From the BTA (and Dr Lowe has said that these are False Statements and wrote a Rebuttal to them which was ignored)

Overwhelming evidence supports the use of Thyroxine (T4) alone in the treatment of

hypothyroidism. Thyroxine is usually prescribed as levothyroxine. We do not recommend the prescribing of additional Tri-iodothyronine (T3) in any presently available formulation, including Armour thyroid, as it is inconsistent with norm

al physiology, has not been scientifically proven to be of any benefit to patients,

and may be harmful. (f) There are potential risks from T3 therapy, using cur

rent preparations, on bone (eg osteoporosis) and the heart (eg arrhythmia). We note

that the extract marketed as Armour thyroid contains an excessive amount of T3 in relation to T4. Over-treatment with T4, when given alone, has similar risks.

dashi2208 in reply to shaws


I'm taking NDT and from what I gather from above you don't recommend it as a effective treatment. I wonder what it is that you do believe to be the most effective treatment?

shawsAdministrator in reply to dashi2208

The above is an excerpt from the the British Thyroid Association who have withdrawn NDT. They are not scientists and as Dr Lowe stated, they have made False Statements about NDT. I did not say I didn't recommend it after all it is the very original and people were diagnosed upon symptoms alone and no blood tests which meant that people were dosed according to symptoms until they were relieved. I would certainly prefer it to levothyroxine.

Dr Lowe, one of our advisers only prescribed NDT or T3 alone.

humanbean in reply to shaws

Shaws said "T3 is very expensive".

I would quibble with that. It is very expensive for the NHS. In several countries in Europe it can be bought for a few euros a box, over the counter without a prescription.

Going back to the OP, having taken T3-only myself for about 10 weeks I would say that it can be a bit of a rough treatment for some people. It has a short half-life and if you need to dose in small amounts several times a day it is like being on a rollercoaster - up and down in energy, mood, headaches/not having a headache, having palpitations or not etc.

But if people add in a little T4 AND can convert it readily to T3 AND transport it into the cells properly then it can smooth out the bumps because the body converts as necessary. But if someone can do that then there may not be much need for T3 in the first place. But, very few people on this site are likely to live in a world where they convert readily and transport it properly, which is why people often don't like T4-only.

Hope that makes sense. :)

shawsAdministrator in reply to humanbean

Re T3 short half life - this is a quote from Dr Lowe:-

January 30, 2002

Question: I’m a physician who has just begun using T3 in my practice. One thing I’m concerned about is the short half-life of T3. Shouldn’t patients divide their daily dose up and take part of it at least twice each day, or instead use sustained-release T3? It seems that this would allow the effects of T3 to continue through the day rather than stop midway or in the evening?

Dr. Lowe: The short time that T3 is in the circulating blood isn’t the limit of its beneficial effects on the body. When T3 binds to T3-receptors on genes, the binding regulates the transcription of mRNAs, and the mRNAs are later translated into proteins. The transcription and translation initiated by the binding of T3 to T3-receptors occur in waves, and these waves far outlast the T3 that started them at the chromosomes. Moreover, the newly synthesized proteins themselves far outlast the transcription and translation. As a result, a single dose of T3 will be long gone from the patient's system before he or she experiences most of the benefits of that dose—a molecular and metabolic yield that may smoothly spread out over one to three days. The "rocky road" ( August 7, 2001)



Third, the leaflet on Cytomel pharmacies give patients when they fill their prescriptions states, "POSSIBLE SIDE EFFECTS: NO COMMON SIDE EFFECTS HAVE BEEN REPORTED with proper use of this medication." This information is accurate—when plain, full-strength, one-time-per-day doses of T3 are used properly, there are no adverse effects. The only adverse effects occur when a patient takes a dosage that for her is excessive.

When I was on T4 and T3 I still felt rotten and after much reading I suspected that I was converting the T4 into reverse T3 (my Dr wouldn't test for reverse T3 so I have no proof other than symptoms) so I stopped taking the T4 and am slowly feeling better abd less like a grumpy hibernating bear.

Everdean in reply to joboise

Yes I experienced improvement when I stopped T4 and just stayed on T3. But still working at it as I think there is room for more improvement. Thanks .

You may also like...