The hypothyroidism is a common endocrine condition in which there is inadequate production of thyroid hormone or suboptimal action of thyroid hormone in target tissues. Hypothyroidism affects the cardiovascular system, the skin, the neurological system, causes menstrual disturbances in women, etc. At the digestive level, there are frequent gastrointestinal motility disorders related to a motor dysfunction of the intestine, so it is typical that hypothyroidism causes constipation.

Reduced motility or slow transit is one of the risk factors for the development of small intestinal bacterial overgrowth (SIBO). Thus, it has been described that SIBO may be present in more than half of patients with hypothyroidism. (1). In fact, a predictor of SIBO in patients with hypothyroidism could be diarrhea, since diarrhea is an infrequent symptom in these patients, but it is very common when SIBO is present (2).

Therefore, although chronic gastrointestinal symptoms may go unnoticed in hypothyroidism, due to the existence of other systemic symptomatology involving the cardiovascular, neuromuscular or ophthalmic systems, and because gastrointestinal motility is altered, which may cause SIBO, it would be advisable that patients with hypothyroidism be evaluated for bacterial overgrowth due to hypomotility. which may cause flatulence, bloating and/or abdominal pain, or diarrhea.

 

  1. Lauritano EC et al . Association between hypothyroidism and small intestinal bacterial overgrowth. J Clin Endocrinol Metab. 200; 92(11):4180-4.
  2. Goldin E and Wengrower D. Diarrhea in hypothyroidism: Bacterial overgrowth as a possible etiology. J Clin Gastroenterol. 1990;12:98-9.