Seeing the endocrinologist soon for thyroid and B12 problems

Dear All,

I'm new here and I wanted to ask this community about what I need to ask the endocrinologist when I see him soon. I have been posting over on the Thyroid UK site. In brief, I had been on 150mg levothyroxine for 20 + years with no problems. I had flu in March/April 2016 which sparked a health crisis with neurological symptoms (peripheral neuropathy, pins and needles, burning sensations, headache, nerve pains, twitches in my legs etc). I hade a number of rapid changes of levothyroxine dosage. I have now been on 125mg for the last 4 weeks, bloods being done tomorrow.

I was getting worse and worse until I started supplementing 1000mg sublingual methylcobalamin + a B complex supplement on 2nd July. This had an immediate effect in reducing and eradicating some of the worst symptoms and I have made slow, steady progress to date. I have had quite a lot of nerve damage in my legs. I still get some nerve twitches but they are much reduced.

My GP says I don't have PA because my MCV was 'normal' (88.8 range 77-100). My serum B12 tested at 452ng/L. The widespread advice about supplementing B12 if below 500 informed my decision to start supplementing. I have since read the British Society for Haematology's 2014 Guidelines for the diagnosis and treatment of Cobalamin and Folate disorders, which recommends further tests and trial dosage of hydroxocobalamin when there is a 'strong clinical suspicion of cobalamin deficiency' based on symptoms in cases greater than 200ng/L .

I feel like I have been giving myself a replacement dose of B12 but have never received a 'treatment' dose that addresses the neurological symptoms. Are the intramuscular injections more effective than oral doses? Presumably oral supplementing wouldn't have worked if I had PA? Or could I have been absorbing the B12 via my mouth rather than in the gut? Presumably I should ask the endocrinologist to test for Intrinsic Factor antibodies to rule out PA? (Although I see from the guidelines that patients negative for the IF antibodies 'with no other causes of the deficiency, may still have pernicious anemia').

Any guidance very gratefully received.

1 Reply

  • B12 deficiency is either caused by lack of B12 in the diet (eg strict vegan - who doesn't supplement or eat cereals fortified with B12) which is actually quite rare. Or by an absorption problem. Absorption problems include PA but also include

    gastric surgery affecting the ileum (which could include gastric band)

    genetic abnormalities affecting the ileum

    low stomach acidity (something that gets more prevalent with age)

    numerous drug interactions including: metformin used to treat type 2 diabetes, PPIs used to treat high stomach acid (particularly dangerous if the underlying problem is really low stomach acidity mistaken for high stomach acidity), NSAIDs, some anti-convulsive medications and others that are frequently used to treat pain (possibly neurological symptoms misdiagnosed eg as fibromyalgia.

    Another potential cause of B12 deficiency is liver damage - B12 is normally stored in the liver and this is critical to the bodies ability to recycle B12 which keeps normal daily requirements very lowl

    Given that you have been taking very high doses of B12 but they haven't had much effect on the levels in your blood - it would seem most likely that you have an absorption problem. Oral can be effective for some people - partly because 1% is absorbed outside the ileum - passive absorption - and possibly also because malabsorption doesn't actually mean no absorption so there may still be some getting through in the ileum. Injections will be a much more efficient way of getting B12 into your blood as it is by-passing all the absorption problems in the gut. If the tablets were sublinguals then it is probable that you were absorbing through membranes in the mouth rather than the gut so that could be part of the story as well.

    Nerve damage takes a long time to heal and in some cases may be permanent - one reason why a B12 deficiency really needs to be addressed quickly if there are neurological symptoms.

    Your GP is, unfortunately, one of the many who really doesn't understand B12 - how it works and hence how a deficiency works. There is no guarantee that your endo will be any better. B12 is used by a number of systems in the body - including the processes that create healthy blood cells (which is how it leads to macrocytosis), the processes that maintain the protective sheath around nerve cells that enables them to communicate properly, the processes that release energy in cells and processes that go on in the brain. Whilst macrocytosis is a very common symptom it is certainly not the cause of all the other symptoms nor is it a defining characteristic and significant numbers of people will have neurological and neuropsychiatric symptoms long before any anaemia develops. - I suffered 40+ years of depression and anxiety - 25+ years of neurological problems and yet my GP thinks that the deficiency was caught early because I don't show any signs of macrocytosis.

    If you are supplementing folate/folic acid then there is a good chance that that will counteract against the appearance of macrocytosis.

    Suggest that you look through the materials in the pinned post

    and also these materials prepared by another member of the forum fbirder

    and go prepared to with copies of them to share with the endo.

    Unfortunately the fact that you have supplemented will make it difficult to test further to confirm that you have a B12 deficiency as it will skew the results of test. I know that they recommend supplementation on the TUK forum but ideally you should get a diagnosis first ... though I also recognise that this can be extremely difficult - one of the materials on the pinned post is an article by the dutch equivalent of the PAS highlighting the dangers of supplementing before diagnosis.

    IFA is not a reliable test. Personally I think the advice to look for a cause, which focuses on PA is not really that helpful. Most of the tests don't actually rule out PA ... and whatever the cause of an absorption/retention problem the treatment would be the same so it seems to me that the current advice can lead to a journey into madness.

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