If you are taking levothyroxine- commonly known as Synthroid- to treat your under-active thyroid (hypothyroidism) you could be increasing your chances of developing Small Intestinal Bacterial Overgrowth (SIBO).

SIBO is defined as an increased amount of bacterial growth in the small intestine. Symptoms of SIBO overlap with Irritable Bowel Syndrome (IBS) and include bloating, abdominal pain, diarrhea and constipation.

To investigate the relationship between hypothyroidism, Synthroid and SIBO, researchers retrospectively pooled 1809 patients who had undergone SIBO hydrogen breath testing and analyzed their clinical data to identify possible risk factors.

From their statistical analysis, they concluded that among other factors, hypothyoidism and Synthroid use were the most strongly associated to SIBO. Surprisingly, Synthroid therapy was found to be a stronger predictor of SIBO than hypothyroidism alone.

In other words, hypothyroidism is connected to the development of SIBO, but it’s supposed treatment, Synthroid, is actually even more connected.

It’s clear why hypothyroidism and SIBO would go together. It is thought to slow small intestine motility, which allows bacteria time to grow, causing the uncomfortable IBS-like symptoms. While Synthroid is commonly prescribed to correct hypothyroidism, it doesn’t seem to affect the SIBO problem. In fact, it may actually contribute to it. The reason for this is still unknown.

Ask your health care provider for SIBO testing if you suffer from digestive discomfort and have been diagnosed with hypothyroidism. This is especially important if you take Synthroid.

At Healthflow, we test for SIBO using the 3-hour hydrogen and methane lactulose breath test. For more information, book your free 15-minute Meet & Greet today.

References:

Brechmann T, et al. Levothyroxine therapy and impaired clearance are the strongest contributors to small intestinal bacterial overgrowth: results of a retrospective cohort study. World J Gastroenterol. 2017 February 7; 23(5): 842-852.