Iron and Thyroid Hormone Replacement: Can low... - Thyroid UK

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Iron and Thyroid Hormone Replacement


Can low iron explain why one might have optimal thyroid blood results but still be getting symptoms? Or would your bloods not be optimal if the cause was low iron? Does low iron stop the cells from using the hormones? I know low iron in itself can cause symptoms but i have always had low iron and not always felt like this.

10 Replies

Without results and ranges we can't really help you. Unless your results are optimal according to thyroid UK then they aren't optimal.

However yes if you have another medical condition and have low iron then you will feel worse.

In the case of any medical condition which involves the metabolism e.g. hypothyroidism or involves the immune system e.g. Hashimotos then having low iron will make you feel a lot worse. In short low iron slows down the metabolism and leads to a weaker immune system.

it is also a good idea to have your vitamin D,folate and vitamin B12 levels checked as if any of these aren't optimal then that is another reason you feel terrible.

hw7342 in reply to bluebug

Hi Bluebug thanks for looking. I posted my results in August and i think you did reply to me then under my post 'shocked at my BH results' so thank you for that too. I was waiting to see if symptoms were lagging behind good bloods really but still no difference in my fatigue. So i was wondering if low iron stops the cells receiving whats in the blood. Its all so confusing and complicated. Particularly as my iron has fallen since then too from 28 down to 20.6 (20-150 ug/L) despite supplementation. My antibodies which had fallen a bit have also gone back up again. B12 is now above range which is ok, folate in top third, not sure about D but it was in the 80's and i have been supplementing a bit since.

bluebug in reply to hw7342

The other posters in that post pointed out that you aren't converting T4 to T3 properly which would explain why you have difficulties getting your iron up as you have autoimmune thyroid disease.

Have you tried adding T3 or NDT to see if that helped?

Your test results don't have a vitamin D level in them - you need to get this tested if you haven't in the last year, and now is a good time to do it in the year. I know myself I couldn't get my iron level up when I was severely vitamin D deficient. Once my vitamin D level was over 70nmol/L I had no problem. Again vitamin D is involved in metabolism and the immune system and is also important for the thyroid. Oh and be aware a tan stops you from absorbing vitamin D as easily.

hw7342 in reply to bluebug

My FT4 was 22.24 slightly over range and my FT3 was 6.05 slightly below top of range... i don't think anyone was saying that i had problems converting. My vitamin D is not on there no, it was done on 1st of july with my gp surgery and was 82. Yes i have tried adding a bit of T3 since those august results which has led to my FT3 being slightly over range. I felt amazing at first only for first few hours after taking it but now just feel fatigued all the time. I am reducing my levo down from 75 to 50 this week.

bluebug in reply to hw7342

I've just been though your old posts.

If you are having frequent periods and/or heavy periods then your ferritin levels will be lower and will start falling if you can't absorb enough iron to replace what you are losing.

Doctors on the NHS tend not to be concerned unless your haemoglobin level falls under the lower boundary of the NHS lab range, this can be 11.5g/dL in many areas. (The World Health Organisation (WHO) set a level at 12g/dL)

And while there is a direct link between low ferritin and iron deficiency anaemia . This explains it better - Many NHS labs have a ferritin range that starts at 6 or 7 for pre-menopausal women. In other words by the time they realise something is wrong with your ferritin level you are likely to have iron deficiency anaemia. (The WHO set a level of 15 for ferritin.)

Anyway the standard treatment for low iron is prescribing a course of iron tablets and then to put you to go on the pill/ have a coil fitted as these are suppose to make periods lighter. Unfortunately in some women this doesn't alter the bleeding plus the pill/coil has bad side effects.

The standard treatment then is to refer you to a gynaecologist, and if the gynaecologist can't treat you to a haematologist. Be aware because you have hypothyroidism the GP will want to refer you to an endo first as period "problems" are also linked to hypothyroidism. However the endo can't help you if your thyroid hormones are optimal, and as most of them specialise in diabetes anyway they will just think being in range is OK.

Often the advice from the haematologist if they don't find anything wrong apart from heavy bleeding/frequent periods is to take iron tablets continuously until the menopause at a dose higher than the RDA and to be tested frequently to ensure you don't have iron deficiency anaemia.

As ferrous fumerate gives you painful gut problems and diarrhoea and your level is falling I would go back to the GP, and tell them all this.

They can prescribe you a different iron salt - they will probably try ferrous sulphate before prescribing one of the more expensive ones IF they look it up in the British National Formulary. Link -

Some can't be bothered and won't prescribe anything different because they think they can't be they are allowed to or they can refer you.

Hidden in reply to bluebug


Would you mind posting - or PM me - the optimal results according to Thyroid UK? That would really be great for future reference. Or can they be found elsewhere here on HU? I apologise for my ignorance.


Yes, yes and YES ....

Iron is a common mineral deficiency in hypothyroidism due to gut malabsorption issues (hypochlorhydria.) Anaemia symptoms can match those of hypothyroidism (fatigue, palpitations, brain fog, dizziness, etc).

Deiodinase is a peroxidase enzyme that is involved in the activation (or deactivation ! ! ) of thyroid hormone. Iron is key for conversion of T4-T3 (active hormone) and low levels may decrease deiodinase activity resulting in conversion to reverse T3 ( rather than the active hormone). This means you could be hypothyroid (with low ferritin) and yet appear “normal” according to the standard TSH and T4 thyroid labs.

Low ferritin can also be indicative of a later full blown anaemia before the red blood cell count begins to decline.

Thyroid medication can bind to certain types of iron supplements making the thyroid medication less effective so space them four hours apart.

hw7342 in reply to radd

hi radd thanks for the informative reply. My T3 was right at top of range at 6.05 so i am guessing this means that conversion is good and that my low iron is not affecting things. thank you.

radd in reply to hw7342


Test results may show optimal but this is only the amount in the blood stream and not the amount that is working on an intracellular level.

Iron deficiency can reduce T4 to T3 conversion and yours is at top of range but I would still consider an iron deficiency to block the thermogenic (metabolism boosting) properties of thyroid hormone resulting in diminished intracellular T3 levels and possible hypo symptoms.


Iron Deficiency Altered Triiodothyronine Activity


Iron Deficiency Impairs TPO Activity.

hw7342 in reply to radd

thank you so much

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