Your gut is home to 70% of your immune system in the form of gut associated lymphoid tissue (or GALT as it is affectionately known). GALT is VERY important and acts like a larder for storing part of your immune system’s defence system, immune cells. Immune cells, like T and B lymphocytes are deployed to defend you against potential threats and in the case of Hashimotos, immune cells attack self.
But what does this mean for thyroid health? We were struggling to see the link too, but let us explain. Your immune system can be triggered through something going on in your gut, take leaky gut (we aren’t just talking the normal leakiness we all get), stuff can get through that shouldn’t and so your body amounts an immune response. If a thyroid condition has your immune system working overtime, this can have a negative effect on your gut health.
Converting hormones into the useful ones
Some T4 actually gets converted into the active T3 in the gut using an enzyme, intestinal sulfatase which comes from your beneficial microbes! If your gut is out of whack (commonly termed dysbiosis – see our infographic above), it may reduce the conversion of the inactive T4 to the active T3.
The state of your gut and its microbes can also influence the absorption of micronutrients like iodine, iron and copper, which you need for thyroid health. Your microbes have the ability to increase the bioavailability of iron in the gut by producing short chain fatty acids. Your gut microbes also regulate how much iodine you use and how it is broken down and circulated in the body. Iodine is essential for thyroid health. Inflammatory bowel disease can also impair iodine absorption.
When we are stressed, we produce more cortisol (aka your stress hormone), which may also reduce the amount T3 (the active thyroid hormone). Stress comes in all shapes and sizes, perceived or actual, but one source is your gut. Inflammation in your gut, whether through dysbiosis, immune response or gastrointestinal disease, will increase circulating cortisol, which if prolonged can have a negative effect on your T3.
Low thyroid function can slow down how often you go. We know that transit time is linked with diversity of gut microbes. Constipation comes with its own issues, in particular, the effect on circulating oestrogen levels, which may affect fertility and menopausal symptoms.
Your gall bladder is a bit of an unsung hero. It stores bile. Bile regulates metabolism through changes in thyroid hormones and helps you digest and absorb fats. Research has shown that in those with hypothyroidism, bile acids levels were reduced. Insufficient bile can impair how well you digest and absorb nutrients and how well your body deals with hormones and toxins that it needs to get rid of.
Research indicates that specific probiotics may be beneficial on thyroid hormone and function and the availability of minerals. We aren’t at a point to conclusively say which strains do what so more research is needed.
Be wary of claims that fixing your gut will fix your thyroid. It simply isn’t that simple and there are so many other factors that play a part. A lot of the research has been done in animals (rats mostly) and us humans are rather different to them! We need bigger trials on humans to understand the complex relationship between thyroid health and gut.