Does low ferritin cause low FT3?

Hi all

I saw my Endo last week who told me my TSH was 0.02 and my FT3 was 4 and I can't remember what my FT4 was( waiting for my GP to give me results on a print out) but she was more concerned my ferritin has reduced to 24.

I'm on 100mcg of Levo and 12.5 of T3 and take 300mg of Ferrous Gluconate along with VitD and K2, Selenium, B12, magnesium and Zinc ( not all at the same time ;) )

I wanted to increase my T3 med but she doesn't want me to. She has told me my ferritin should be in treble figures and to take 600mg of Ferrous Gluconate to get my levels up. I'm hoping this is why I'm so tired :( I do take VitC with my Iron tablets to help absorption. I can confirm that I am a veggie and therefore will not eat meat or liver.

By increasing my ferritin levels will this help me to increase my FT3 levels?

10 Replies

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  • It could possibly increase your conversion of T4 to T3. And, it could increase the amount of T3 that gets into the cells. But, not necessarily. Do you have a range for the FT3?

  • Hi GG

    No I'm waiting for a copy of the results from my GP.. I think I now just scrape into the 'normal' range from my FT3.

  • Well, if your FT3 is low, your doctor is wrong not to increase it. There's no reason why she shouldn't do that as well as improving your ferritin.

  • The good old TSH is low enough and increasing my T3 med will make my TSH undetectable!! Honestly I hate TSH and all it stands for! She has told me to get a check up for Ferritin with my GP in a months time and I'm seeing her again in 6 months. I have a good mind just to increase my T3 by 6.25mcg to see if it makes a differences in the next few weeks.

  • Well, I would, if I were you!

  • A note on your dose of iron supplement.

    600mg of ferrous gluconate will contain 70mg of pure iron. See the table on this page.

    evidence.nhs.uk/formulary/b...

    Just for comparison, when I was low in iron I was initially prescribed ferrous fumarate 210mg, one tablet, three times a day. The total iron content of that per day was 207mg pure iron per day.

    Ferrous fumarate 210mg (and the other iron types listed in the link above) can be bought online or in UK pharmacies without prescription. After my initial prescription ran out I started buying my own.

    So, you could increase your iron dose quite dramatically if you wanted to. (It is always the pure (elemental) iron level in iron supplements that it the important thing to know.) Whenever people take iron supplements they should be tested regularly to avoid poisoning themselves. Unfortunately nobody knows in advance how fast they will absorb iron, so some trial and error and caution is required.

  • Thanks for that... I have been taking two tablets mid morning.. I'll start taking three and spread them over the day/ evening and ask my GP for a blood test in one months time..

  • Did you take Vit C with each dose of Iron? I take a half a teaspoon of Ascorbic Acid with my Iron tablet and I'm wondering if it's okay to take 1 and a half teaspoons of Vit C in a day

  • I don't know of any problems you would get from that dose of vitamin C. The worst that is likely to happen is that you might get diarrhoea.

    I always take vitamin C with iron.

  • Hypothyroidism can cause low ferritin. As far as I can see low ferritin does NOT stop T4 to T3 conversion, in spite of speculative claims that it does. Using a bit of common sense (usually verboten in endocrinology) if this were so we would expect all anaemic patients to suffer from hypothyroidisim and of course they don't.

    Also, the pituitary relies upon T4 to T3 conversion to suppress the TSH. So unless your fT4 is at a reasonable level AND your TSH is high then you are converting and low ferritin is not stopping conversion.

    If you have hypothyroid signs and symptoms and low ferritin in spite of iron supplementation then there is a chance you are clinically hypothyroid and this is keeping your ferritin levels low. i.e. low ferritin can be a marker for hypothyroidism. In this case if your fT4 is reasonable I'd supplement with L-T3 and accept a low TSH - whilst taking care to avoid overtreament.

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