This is a useful paper showing low B12 is associated with hypothyroidism. Another paper indicating vitamin deficiency that needs treating. And that GP's should know about it.
Vitamin B12 levels in thyroid disorders: A systematic review and meta-analysis
Vicente A. Benites-Zapata, Felipe L. Ignacio-Cconchoy, Juan R. Ulloque-Badarac, Enrique A. Hernandez-Bustamante , Esteban A. Alarcón-Braga, Ali Al-kassab- Percy Herrera Añazco
Abstract
Numerous studies have found an association between vitamin deficiency and thyroid disorders (TD). The presence of anti-parietal cell antibodies is indicative of reduced ability to absorb vitamin B12. Thus, this study reviewed the existing studies with the objective of assessing differences in the serum levels of vitamin B12 among patients with and without TD, the frequency of vitamin B12 deficiency in patients with TD, and the presence of anti-parietal cell antibodies in patients with TD.
Methods: A meta-analysis of random-effects model was conducted to calculate pooled frequencies, mean differences (MD), and their respective 95% confidence intervals (CI). We identified 64 studies that met our inclusion criteria (n = 28597).
Results: We found that patients with hypothyroidism had lower vitamin B12 levels than healthy participants (MD: −60.67 pg/mL; 95% CI: −107.31 to −14.03 pg/mL; p = 0.01). No significant differences in vitamin B12 levels were observed between healthy participants and patients with hyperthyroidism (p = 0.78), autoimmune thyroid disease (AITD) (p = 0.22), or subclinical hypothyroidism (SH) (p = 0.79). The frequencies of vitamin B12 deficiency among patients with hypothyroidism, hyperthyroidism, SH, and AITD were 27%, 6%, 27%, and 18%, respectively
.Conclusions: Patients with hypothyroidism had lower levels of vitamin B12 than healthy participants. No significant differences were observed between vitamin B12 levels and hyperthyroidism, AITD, or SH.
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diogenes
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Thank you, interesting. I still haven't been able to clarify anything regarding Dr Chandy's proposal that B12/folate deficiency affecting myelin will increase likelihood of pituitary signalling misfiring, potentially causing central/secondary hypo, and we also have to consider that B12 testing is flawed so just looking at those with 'low serum B12' will miss a section of those with B12 deficiencies, particularly those of metabolism. It would be a start if anywhere would actually test GPC antibodies. Best wishes
I don't quite understand. If as a hypothyroid patient I am 27% more likely to have low B12, how do I find out definitively if I do? If there are absorption issues will serum levels be indicative or not? I am taking a B12 complex but is it getting into the cells?
Probably not..You need Gut microbiome and genetic testing done... I only found out this information from Eduardo Patrick.....90% chance of having Leaky Gut Syndrome
Active testing may show deficiency in some people who are missed with straight serum testing, but is also not infallible, hence need for IF ab, GPC ab, MMA, homocysteine etc. There is no definitive test - all of those can look ok and you can still be deficient. B12 metabolism is strongly genetic and there are a lot of places where things may be going wrong, over and above the flaws in the tests themselves.
One of the main problems Musicmonkey is that, according to the BMJ research document, there is no reliable test for PA/B12def. Therefore, it seems neuro/psychiatric symptoms could be the most reliable guide to diagnosis, eg:
Relentless fatigue, dizziness, brain fog, memory problems, proprioception (balance), tingling or numb toes, fingers, unusually angry outbursts, paranoia, etc.
Plus gut problems, H/pylori
Vegan, vegetarian, low meat diet
Age over 60 years
Extreme stress or overdoing exercise seems to exacerbate symptoms and many drugs - Metformin, PPIs, etc - can also further deplete B12
………..
Re. the connection with Thyroid Disease, I believe it was Martyn Hooper, Chairman of the Pernicious Anaemia Society, who wrote in his latest book that there is a 40% chance those with TD go on to have B12def. PA, and vice versa……..
Even though four in our family have both TD and B12 deficiency, one of the main difficulties is unreliable testing, which in today’s climate of mainly test based medicine, is further exacerbated if already supplementing B12…..
This is why so many of us on the PA forum resort to self-treatment to stay sane !
"Our findings are particularly useful in clinical settings as they emphasize the necessity of in-depth evaluations of vitamin B12 levels in patients with TD. Nearly one in four patients with either SH or hypothyroidism suffers from B12 deficiency. Although it is tempting to suggest routine vitamin B12 assessment in patients with TD, more studies are needed to support this practice.
There is still scarce evidence suggesting that the administration of vitamins with antioxidant properties in patients with TD, such as hyperthyroidism, can decrease the severity of clinical symptoms (94). Likewise, some studies suggest vitamin D supplementation can have a beneficial effect on bone system among these patients (94). Nevertheless, the role of vitamin D is controversial. A systematic review revealed that although there are various health benefits of dietary supplements in the prevention and treatment of several TD, there are also many risks associated with the use of these supplements (95).
In this regard, clinical practice guidelines should include nutritional assessments as part of the management of TD patients. We found that many of the current guidelines on TD do not require a comprehensive nutritional evaluation as part of their management plan, nor do they recommend assessing and addressing B12 deficiencies (96–98)."
Is it safe to assume that by "patients with hypothyroidism " below , they mean:
~'patients who are currently hypothyroid with low T4/ high TSH (and possibly low T3)'
as opposed to:
~ 'patients who have a hypothyroid diagnosis and are now (allegedly) treated'
"Conclusion
Patients with hypothyroidism had lower levels of vitamin B12 than healthy participants. No significant differences were found between vitamin B12 levels and Hyperthyroidism, AutoImmuneThyroidDisease, or Subclinical Hypothyroidism"
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Vit B12 and other levels
Hypothyroid, T3 levels vastly off
Hypothyroid & low B12 - painful feet
Cholesterol levels going up with Hypothyroidism 
b12 levels high and serum ALT 
