The SIBO-Thyroid Link
The thyroid gland is a powerhouse in the human body. But because a lot of it’s magic happens behind the scenes in the endocrine The more we grow to understand our bodies, the more we realise how interconnected they are. Not just by neurological pathways or special organ systems, but how more often than not, one condition can impact another. There are times it truly does feel like you can’t do anything right, that the more you try to fix one thing the more you realise that there is ‘wrong’ with you. But that couldn’t be further from the truth. Our bodies are complex, multi-talented organisms. When we think about everything that has to go right to even keep us alive, it’s mind-blowingly humbling. But a deeper understanding of the nature of our interconnectedness is sometimes what we need to address our body’s biggest concerns. There’s one I see often within the clinic, where many clients don’t know the underlying cause of their condition. That’s why I have taken the time to help you understand the complexities of a condition known as SIBO and how it can be a driving factor in thyroid conditions.
What Is SIBO
It sounds serious, and if left undiagnosed there can be some long-term cascading health concerns, but SIBO can be easily addressed. SIBO stands for small intestinal bacterial overgrowth, which comes from over-colonisation of bacteria in the small intestine. Unlike the colon, the small intestine typically has a low count of organisms (10,000 per millilitre - which I promise is small in the scheme of things). The cause of SIBO will differ between individuals, but common symptoms often immediately include nausea, bloating, vomiting, reflux, and either constipation or diarrhoea, and over time increase to malabsorption, malnutrition and weight loss, which is caused by a number of miscommunicating mechanisms within the body. Some other symptoms of SIBO include loss of appetite, abdominal pain, an uncomfortable feeling of fullness after eating, feeling bloated even after consumption of water, waking bloated and excessive flatulence.
Long-Term Impacts of SIBO
When our bodies spend too long trying to overcompensate for SIBO, the symptoms may develop into more worrisome conditions. Over time, the bacterial overgrowth alters the structure and function of the small intestines - particularly the cells that line the walls. This is how malabsorption begins to occur, which can lead to widespread deficiencies throughout the body. Over time, SIBO can also begin to impact thyroid function.
SIBO & The Thyroid
These two are like the friends who love to hate each other. They both feed off the other, with each cycle likely worsening the conditions. Gut health and thyroid health are intrinsically connected by nature; around 20% of thyroid hormone conversion takes place in the gut, and the gut is believed to house 70-90% of the immune system, depending on what research you're reading. As thyroid disorders are almost always autoimmune conditions, this connection is important. In the instance of hypothyroidism, a slow metabolism will ultimately lead to slow digestion. Malabsorption of key nutrients in SIBO needed for thyroid hormone production and conversion can also lead to reduced thyroid function.
Low Thyroid Function & Peristalsis
Coupled with a slower metabolism, frequent constipation is another symptom of hypothyroidism. As food and wastes begin to move through the digestive tract more slowly, bacteria is likely to multiply throughout the small intestine. The thyroid is responsible for our hormone signals that stimulate the wavelike action, peristalsis. This metabolic action is crucial for moving food and wastes through the digestive tract and eventually eliminating them from the body. If it’s not functioning properly, digestive transit is much longer and there is ample opportunity for a bacterial overgrowth to occur.
Low Stomach Acid & Hypothyroidism
Another stress on this relationship is hypothyroidism’s impact on stomach acid. People living with hypothyroidism often have lower levels of stomach acid, known as hydrochloric acid (HCL). HCL is crucial for helping the gut break down foodstuffs, yet T3 (the active thyroid hormone) is needed by the parietal cells (the epithelial cells that line the outer walls) of the stomach to produce acid. This acid acts as a first line of defence from the outside world as it helps to neutralise any food and waterborne bacteria or pathogens. It also helps to keep the first portion of the small intestine relatively bacteria-free.
Thyroid Hormone Conversion & SIBO
Studies have indicated that approximately 21% of T3 and T4 (the main thyroid hormones) conversion occurs within the gut. For this process to occur, optimal gut flora and microbiome balance are needed. So for someone living with a bacterial overgrowth within their digestive system, issues may arise with the hormone conversion, potentially leading to hypothyroidism.
Oftentimes we fall into a trap of thinking conditions and disease act on their own, but we’ve come to understand that this isn’t always the case. Thyroid conditions and SIBO are often intrinsically linked by the very nature of their signs and symptoms, but this can be a blessing in disguise, because by identifying and treating one, we can begin to support the other.
If you suspect you may have SIBO, or you’re suffering from the symptoms, and would like to discuss your current health in more detail, why not book in for a free 15-minute consultation? This will allow you to ask questions about what to expect and how a naturopathic approach can support your health needs.
Melissa Briggs is an experienced Brisbane based Naturopath with a particular interest in women’s health and thyroid disorders. Need help with your health? Get in touch here.