03/19/2026
Hypothyroidism slows gut peristalsis and lowers stomach acid, increasing the likelihood of constipation and bacterial overgrowth.
“Your digestion slows down when your metabolic rate slows down from hypothyroidism, and so your stomach becomes sluggish, doesn’t secrete much and doesn’t move fast enough.
People might might eat a carrot today and it might not come out for four or five days.
That’s what happens with hypothyroidism, and speeding up your digestion and secretions, it should be so active streaming fluid from your stomach and pancreas and liver should wash your whole small intestine clean so that no bacteria can thrive in it.” — Ray Peat
“GI symptoms may be ignored in hypothyroidism due to other systemic symptoms of involving cardiovascular, neuromuscular or ophthalmic systems. GI motility is disturbed in hypothyroidism, which can lead to SIBO. SIBO may be responsible for chronic GI symptoms in these patients. It is prudent to evaluate the possibility of SIBO in patients with chronic GI symptoms in hypothyroidism.” — Link between hypothyroidism and small intestinal bacterial overgrowth