Possible Issue Converting FT4 to FT3: I’m posting... - Thyroid UK

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Possible Issue Converting FT4 to FT3

Flatdanny profile image

I’m posting this for a good friend of mine who had been struggling with his hormone health for years. He’s in a bad way and I’m trying to help as best I can becuase his doctors seem to be doing a very poor job. (Harley Steet doc)

He seems to have both low testosterone issues and also thyroid.

He suffers from extreme fatigue and has to take naps every afternoon and has very bad brain fog and struggles to get anything done. He has gained weight too.

Here are his details…

Age: 55

Height: 6’

Waist: 38/40

Weight: 100kg (22lbs)

Body is on the “solid” side, reasonably muscular even though i dont work out.

Carry fat around my middle, it has increased significantly in last couple of years but i put that down to too much wine/beer.


Had glandular fever in my teens. Always been relatively low on energy and had long standing problems with concentration/brain fog. Would say i always had a relatively low sex drive. Have suffered several episodes of high anxiety which resulted in anti-depressants. In recent years had a tendancy to mild depression as well. Diagnosed with CFS and get exhausted by 2 hours of mental exertion (working, concentrating, talking with people). Mental fatigue is worse than actual physical fatigue, can still ski for a few hours a day. Often feel very light-headed and can become irritable easily.

Diagnosed by an endo with -

Hypogonadotrophic hypogonadism

Borderline secondary hypothyroidism

Post viral fatigue syndrome (Epstein Barr virus)

Multi nodular thyroid goitre (no suspicious features)

Short synacthen test suggested abnormal adrenal function but a test of Hydrocortisone didnt make me feel any different.

Meds he’s taking -

Take nebido every 10/11 weeks - normal does of 1000mg/4ml

150mcg Thyroxine (also been suggested to try T3)

Started testo gel approx Mar 2015 and switched to Nebido in May 2015

Started Thyroxine Jul 2015 on around 50mcg and built up to current does of 150mcg

Dabbled with 5 mcg of T3 twice a day but didnt notice anything

Bloods (see image attached)

* I have asked him to start taking his oral body temperature when waking up in the morning and mid afternoon to get an idea of how his overall thyroid is functioning. So far his temps are low pointing to thyroid issues. (36.2-36.5 morning and 36.2-36.6 afternoon)


Would very much appreciate any advice. And especially if he would be better off trying T3 only or combo of T4 and T3.


3 Replies
SeasideSusie profile image

Looking at the November results for thyroid which appear to be with Blue Horizon, the ranges on the spreadsheet for TSH and FT4 are not the ones Blue Horizon use and actually make quite a difference to interpretation of the FT4 result.

TSH: 0.09 (0.3-5.00) - BH range 0.27-4.20

FT4:23.9 (8.80-18.9) - BH range 12-22

FT3:5 (3.1-6.8)

Good conversion takes place when the FT4:FT3 ratio is 4:1 or 3:1. Conversion here is 23.9/5 = 4.78 : 1 so not particularly good.

FT4 is 119% of range, FT3 is 51% through range.

FT4 and FT3 should be in balance near the top of the range, possibly around 19.5 for FT4 and FT3 around 5.9.

It's very strange that he needs to nap every afternoon yet manages to ski for a few hours a day. I don't know where ski-ing comes on the scale of hard exercise, but hard exercises depletes T3 so is that a factor???

My results were similar - over range FT4 with FT3 about 50% through range. I added some T3 to my Levo and I think it might be worth your friend trying this. He will need to lower Levo, initially by 25mcg and add 6.25mcg T3 if self sourced (or 5mcg if prescribed as they are 20mcg tablets). Then it is a matter of taking it slow, gradually increasing T3 by 1/4 tablet each time and keep retesting to keep an eye on levels. FT3 needs to stay in range.

Please note I am not medically trained, my reply is based on my own experience.

Thank you very much for your reply. I did not know the BH ranges were wrong. I will pass on that info to my friend. I will also pass on the info about the conversion ratio and adding the T3.

Not sure about the skiing. Don’t think he goes much to be honest. It’s not a daily thing, just the odd holiday. I know he has to take a nap every afternoon so that’s not normal.

Thank you for your reply. The post is actually all related to my friend but a section of the post was copied over from what he sent over to me so it sounds like it’s referring to me! Apologies for the confusion (;

Yes I’ve heard thyroid and other hormones are linked and often if one has one issue they often have other hormone issues. A double whammy.

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