Author: Dr. Bonnie Brock, NMD, RD, MPH
Poor GI function is increasingly common and one of the major contributors to low thyroid function, which in turn can negatively impact mood, metabolism, cognition and sexual health. Understanding the several important connections between gut health and thyroid function can help you pinpoint areas of your own health that could be improved by addressing the state of your gut.
Dysbiosis- Trillions of bacteria are found in the human intestine, mostly located in the colon, where the two dominant commensal (beneficial) strains are Firmicutes and Bacteroides. These bacteria exist in a symbiotic relationship with you, the host. You provide them housing and food and they play a role in vitamin synthesis (vitamin K, folic acid, vitamin B2, B3, B5, B6, B7, and B12, digestion of dietary fibers, regulation of the immune response and mental health. Pathogenic bacteria are also present in the gut, and when these bacteria become out of balance with the commensal bacteria, it is called dysbiosis. Dysbiosis impairs the healthy microbiota’s influence on the uptake of minerals relevant to the thyroid including iodine, selenium, zinc, and iron. All of them play a role in supporting thyroid function and there is a clear link between thyroid dysfunction and altered levels of these minerals.
Gut Permeability – The presence of dysbiosis over long periods of time can lead to increased permeability of the gut barrier, compromising tight junctions and leading to penetration and exposure of pathogens to the immunoreactive sub-epithelium, promoting inflammation and autoimmunity. Zonulin, a protein that when triggered by gluten or certain bacteria, can be secreted by the small intestine and modulate the integrity and permeability of intercellular junctions. When gluten induces zonulin release, it weakens the connection between the tight junctions and breaks the intestinal barrier. In general, zonulin expression is increased in autoimmune diseases such as Hashimoto’s, the autoimmune thyroid condition.
Constipation – Typical transit time form mouth to elimination of food is 18 to 24 hours. Hypothyroidism slows down the movement of food through the gut by a lack of stimulation to the muscles that control peristalsis. When food is in the gut for extended periods of time, it putrefies, leading to the absorption of toxins and waste by-products. Add gut permeability to constipation, and there can be copious amounts of unwanted molecules passing into the bloodstream and triggering an immune response, leading to an overwrought immune system and eventual auto-immunity.
Poor Estrogen Elimination – Most of the estrogen eliminated from the body is done through the gut. A “slow” gut and dysbiosis leads to the accumulation and toxification of estrogen, which in turn increases breast cancer and uterine cancer risk. In addition, poor estrogen clearance can increase the risk of uterine fibroids, endometriosis, cardiovascular disease, osteoporosis, mood swings, and cognitive decline due to the potential build-up of excess estrogen in the body, which can disrupt normal hormone balance and cellular function.
Join us March 20th 2025 in-office at 6 pm for a lecture of the impact of gut health on thyroid health. 13951 N Scottsdale Rd Suite 110 — see you there!
