Why do we still need T4 when taking T3

[carolinegodlonton]

I was doing some reading about the different hormones needed to treat Hashimotos. If one is taking T3 and our levels are optimal, why does the body still need T4 if its only job is to be converted to T3. Is T4 necessary for anything else other than making T3?

[Lalatoot]

No t4 is not necessary for some folks. There are people who are fine on t3 only. But we are all different. Others on here are best on low t4 and high t3. Finally there are those who need high levels of both. It depends on your body.

[NWA6]

I don’t think enough is known yet, or maybe it’s just me that doesn’t know enough yet. When I was taking a high dose of Levo I felt hyper and yet I had low T3. I was fine on this higher dose for 6mths before I felt ‘hyper’.

Ultimately I lowered the dose and added T3 and now feel good but my T4 dropped a little low but my T3 remained high. I had a few symptoms creep in so I added a little more T4 and felt good again.

So for me it seems I need a good balance of both to feel optimal.

[carolinegodlonton in reply to NWA6]

Thanks for your replies. I'm just trying to get my head around the need for T4. Reading loads of papers and books so I hope to get the answer. Isabella Wentz books might give it.

[shaws Administrator in reply to NWA6]

We don't need to take T4 if we're on T3 alone. I have taken T3 alone for a number of years now.

Several researchers have found that many recover on T4/T3 combination when they don't on levothyroxine. When we add or take NDT or add T3 for instance, blood tests don't correlate as they were invented along with T4 i.e. levothyroxine alone. Doses of any thyroid hormone replacements should relieve all symptoms when on an optimum dose (ie. you feel well with no symptoms).

T4 - levothyroxine - is an inactive hormone and has to convert to T3. T3 is the Active thyroid hormone and is required in all of the T3 receptor cells of which we have many. T4 has to convert to T3.

Before levothyroxine (T4 alone) was introduced to replace the original thyroid hormone replacement (i.e. NDT - natural dessicated thyroid hormones) we never had blood tests at all (hadn't been invented) and dose was increased slowly until we had no clinical symptoms.

Nowadays our doses are increased/decreased according to blood tests and no notice taken of clinical symptoms and doctor may stop increasing dose when we still have symptoms or reduce dose due to the TSH.

One of Thyroiduk's deceased Adviser, only took one blood test for the initital diagnosis. He'd never prescribe levothyroxine at all but prescribed NDT (T4/T3/T1 and cacitonin) the original thyroid hormone replacement introduced in 1892) or T3 alone for those who have thyrod hormone resistance.

The main aim of taking thyroid hormone replacements, is to remove symptoms and for the patient to feel well and symptom-free. Maybe this link will be helpful. Doctors used to increase until we had no symptoms but nowadays it all depends on the TSH (from the pituitary gland) and many medical people believe if TSH is 1 or lower that we're taking too much and reduce dose and symptoms return. Many doctors stop increasing when the TSH reaches somewhere within 'normal' range -

naturalthyroidsolutions.com...

[MaisieGray]

It is known that T4 does have other purposes other than simply being a storage pro hormone, I'll see if I can find a previous post I wrote on the subject. I agree with Paula6, we don't know how much is still to discover about it - for instance in recent years more info has been discovered about the role of T2 than was previously known.

[MaisieGray in reply to MaisieGray]

Sorry, I've given up searching through my posts, it's far too tortuous ...... I can remember reading this quote though, although I don't have a reference: "The regulation of actin polymerization by T4 is critical to cell migration in neurons and glial cells and is important for brain development". However, in the abstract of a paper on the same subject, by Leonard & Farwell, it states "Thyroid hormones play an important role in the growth and development of the brain. Central to the proper integration of neuronal circuitry is the ability of the growing neurite to interpret guidance cues during its migration. The action cytoskeleton is especially rich in the growth cone, and is a likely target for thyroid hormone regulation. This brief review summarizes work showing that thyroxine, but not T3, dynamically regulates the polymerization of the actin cytoskeleton in astrocytes. The ability of T4 to enhance actin polymerization, without directly affecting gene expression, has a profound effect on the ability of the cell to interact with laminin, the major extracellular matrix protein in the developing brain. T4 also regulates the formation of key cell contacts with extracellular matrix guidance cues. These processes are likely to participate in thyroid hormone's regulation of brain development." So whilst it's largely above my intellectual pay grade, this would seem to have particular importance during pregnancy since the early foetus is wholly dependent on its mother's T4 until the second trimester.

[Murphysmum in reply to MaisieGray]

I e just come across this post and I agree wholeheartedly with this statement.

Both my boys (well, one still being diagnosed) have adhd, primarily caused by an under developed frontal cortex.

Despite being educated on most things biological I trusted the medical profession to tell me that my thyroid bloods looked good.

I believe if I had been on a higher dose of levo or indeed with added T3 I wouldn’t be adding this comment.

We have no family history of anything “on the spectrum”.

Increasing numbers of kids diagnosed with spectrum disorders... more efficient methods of diagnosis or mothers who’s TSH was normal? 😢

[carolinegodlonton in reply to MaisieGray]

Thanks. What a pity such a complicated disease is so under diagnosed and not enough research done to properly detect and treat such a common ailment. We will all be experts long before any one in the medical world!

[MaisieGray in reply to carolinegodlonton]

Amen to that. And we'll all die wondering why there is such deliberate distain for it amongst the medical fraternity compared with the consideration and resources given to other common diseases.

[nightingale-56 in reply to MaisieGray]

Maybe it is the distain for learning about thyroid conditions that renders doctors helpless (and some useless).

[whatevs]

Personal anecdote - I started having some really bad pains in my hips and leg joints recently which just so happened to coincide with my latest test results which revealed that my FT4 levels had plummeted.

After increasing my Levo by 10mcg-ish the pain has virtually disappeared. You'll also find similar stories on this site.

So I'm not entirely sure what the science is here but some people definitely need both T4 and T3 medication - but exactly what levels of FT4/FT3 seem highly individualised - so it's just a case of trial and error I'm afraid.