This essentially causes the bacteria to “back up” instead of being released during the normal digestive process.
Patients with chronic GI symptoms in hypothyroidism should be evaluated for the possibility of SIBO.
Treatment with antibiotics has been found to be effective in managing the condition.

Verywell / Michela Buttignol
National Institute of Diabetes and Digestive and Kidney Diseases.Graves' Disease.
National Institute of Diabetes and Digestive and Kidney Diseases.Hypothyroidism (Underactive Thyroid).
Patil AD.Link between hypothyroidism and small intestinal bacterial overgrowth.
Indian J Endocrinol Metab.
2012;86(5):419-26. https://www.niddk.nih.gov/health-information/endocrine-diseases/hyperthyroidism
National Institute of Diabetes and Digestive and Kidney Diseases.Hypothyroidism (Underactive Thyroid).
https://www.niddk.nih.gov/health-information/endocrine-diseases/hypothyroidism
Patil, A.Link between hypothyroidism and small intestinal bacterial overgrowth.Indian J Endocrinol Metab.
2014 May-Jun; 18(3): 307309. doi: 10.4103/2230-8210.131155