Metformin Linked To Low Thyroid Function And Heart Disease

| October 30, 2014

Metformin is often viewed by doctors as the ‘drug of choice’ for treating type 2 diabetes, since it is quite effective in reducing blood sugar levels and is assumed to have fewer side effects than other diabetes drugs. But metformin is far from harmless – it depletes the body of vitamin B12, which is essential for heart health and, as I wrote here, it has been associated with an increased risk of heart failure in men. Now, new research has shown that metformin is also linked with an underactive thyroid, a condition that is often a hidden factor in heart disease.

When researchers in Quebec, Canada looked at data on 74,300 patients who received either metformin or a sulfonylurea drug (another common type of diabetes medication) over a 25-year study period, they found that metformin monotherapy was associated with a 55 per cent higher risk of low thyroid function compared with treatment with sulfonylureas.1 This is a big increase in risk, especially seeing that people with type 2 diabetes are already around two to three times more likely to have a poorly functioning thyroid gland than are non-diabetics.

Dr Laurent Azoulay, who led the study, commented, “Given the relatively high incidence of low TSH levels in patients taking metformin, it is imperative that future studies assess the clinical consequences of this effect.” I couldn’t agree more. TSH stands for thyroid-stimulating hormone, which is released from the pituitary gland in the brain and stimulates the thyroid gland (situated in the throat) to produce its hormones. Low TSH means low thyroid function, which has profound and damaging effects on your heart and circulatory system – and of course, cardiovascular problems are one of the primary complications of diabetes.

Low thyroid function, which often goes undiagnosed, affects the heart in several different ways. It can raise blood pressure, contribute to the development of atherosclerosis (hardening of the arteries), cause irregular heartbeat and increase the risks of coronary heart disease (heart attack) and heart failure (when the heart cannot pump enough blood around the body).2 As I mentioned here, it has been suggested that much of the increase in cardiovascular risk in people with diabetes may be attributable to thyroid problems.

So now we have a situation where the most commonly prescribed medication for type 2 diabetes can be linked with an increased risk of cardiovascular disease, the most common complication of type 2 diabetes. Of course, the statistical association revealed in this study is not proof of cause and effect, but it is one more disturbing piece of evidence that metformin is not as benign a medication as some doctors believe. Like all drugs, it is a dangerous, synthetic chemical whose impact on the body is still being revealed – in a massive experiment in which the patients are the guinea pigs.

Get your thyroid hormone levels checked

If you have type 2 diabetes and you are taking metformin, ask your doctor for a thyroid hormone test, especially if you have symptoms such as fatigue, depression, constipation and weight gain, which could be due to an underactive thyroid. And if your test shows that your thyroid hormones are low, follow the tips here for restoring your thyroid function naturally, without taking more drugs.

Metformin is a huge money-spinner for Big Pharma, who will go to any lengths to protect its reputation as a ‘safe’ medication. And finding a ‘silver lining’ by making a virtue of the drug’s side effects could provide a sure way of keeping those profits rolling in. So, given that metformin appears to interfere with normal thyroid function, it was just a short step for a recent study to suggest that it might be ‘repositioned’ as a treatment for … thyroid cancer.3

As well as finding new applications for diabetes drugs such as metformin, the pharmaceutical companies are constantly looking at ways of using drugs developed for other purposes to further exploit the lucrative diabetes market. In my next blog post I want to tell you about niclosamide, a medicine currently used to expel tapeworms, which could soon be hailed as the next ‘miracle’ diabetes drug.

Wishing you the best of health,

Martin Hum
PhD DHD Nutritionist
for Real Diabetes Truth

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  1. Fournier JP, Yin H, Yu OH, Azoulay L. Metformin and low levels of thyroid-stimulating hormone in patients with type 2 diabetes mellitus. CMAJ. 2014 Sep 22 (Online ahead of print).
  1. Danzi S, Klein I. Thyroid disease and the cardiovascular system. Endocrinol Metab Clin North Am. 2014; 43(2):517-528.
  1. Kushchayeva Y, Jensen K, Burman KD, Vasko V. Repositioning therapy for thyroid cancer: new insights on established medications. Endocr Relat Cancer. 2014; 21(3):R183-194.
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Category: Diabetes and Heart Disease

Comments (2)

Testimonials are based on the personal experience of individuals. Results are not typical and the potential benefits of taking any drug or supplement may vary depending on your individual needs and health requirements. Please consult your GP before making any changes to your medical regimen.

  1. Castelli Gianluigi says:

    I read your article with much interest. I have not access to the references you quoted but when you writes that ‘ Low TSH means low thyroid function’this is not always true. Low TSH is often linked to subclinical or clinical Hypertyroidism. Disruption of hypofisis is quite rare in the etiopathogenesis of thyroid hypofunction. Could metformin be responsable for this kind of alteration?
    Thanks in advance
    Castelli Gianluigi MD

    • MartinHum says:

      Dear Dr Castelli,
      Many thanks for your feedback. It is interesting to note that low TSH is also linked to hyperthyroidism. I have e-mailed you separately regarding your question about metformin and disruption of the hypophysis.
      Best regards, Martin Hum