title: Association between hypothyroidism and small intestinal bacterial overgrowth.
abstract: OBJECTIVE
  Small intestinal bacterial overgrowth is defined as an abnormally high bacterial population level in the small intestine. Intestinal motor dysfunction associated with hypothyroidism could predispose to bacterial overgrowth. Luminal bacteria could modulate gastrointestinal symptoms and interfere with levothyroxine absorption. The aims of the present study were to assess the prevalence and clinical pattern of bacterial overgrowth in patients with a history of overt hypothyroidism and the effects of bacterial overgrowth decontamination on thyroid hormone levels.
  
  
  METHODS
  A total of 50 consecutive patients with a history of overt hypothyroidism due to autoimmune thyroiditis was enrolled. Diagnosis of bacterial overgrowth was based on positivity to a hydrogen glucose breath test. Bacterial overgrowth positive patients were treated with 1,200 mg rifaximin each day for a week. A glucose breath test, gastrointestinal symptoms, and thyroid hormone plasma levels were reassessed 1 month after treatment.
  
  
  RESULTS
  A total of 27 patients with a history of hypothyroidism demonstrated a positive result to the breath test (27 of 50, 54%), compared with two in the control group (two of 40, 5%). The difference was statistically significant (P < 0.001). Abdominal discomfort, flatulence, and bloating were significantly more prevalent in the bacterial overgrowth positive group. These symptoms significantly improved after antibiotic decontamination. Thyroid hormone plasma levels were not significantly affected by successful bacterial overgrowth decontamination.
  
  
  CONCLUSIONS
  The history of overt hypothyroidism is associated with bacterial overgrowth development. Excess bacteria could influence clinical gastrointestinal manifestations. Bacterial overgrowth decontamination is associated with improved gastrointestinal symptoms. However, fermenting carbohydrate luminal bacteria do not interfere with thyroid hormone levels.
authors: Internal Medicine Department, Catholic University of Sacred Heart, Gemelli Hospital, Largo A. Gemelli, 8, 00168 Rome, Italy.
authors: Ernesto Cristiano
authors: EC
authors: Lauritano
authors: Anna Lisa
authors: AL
authors: Bilotta
authors: Maurizio
authors: M
authors: Gabrielli
authors: Emidio
authors: E
authors: Scarpellini
authors: Andrea
authors: A
authors: Lupascu
authors: Antonio
authors: A
authors: Laginestra
authors: Marialuisa
authors: M
authors: Novi
authors: Sandra
authors: S
authors: Sottili
authors: Michele
authors: M
authors: Serricchio
authors: Giovanni
authors: G
authors: Cammarota
authors: Giovanni
authors: G
authors: Gasbarrini
authors: Alfredo
authors: A
authors: Pontecorvi
authors: Antonio
authors: A
authors: Gasbarrini
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001419:Bacteria / Q000254:growth & development*; D001944:Breath Tests; D003627:Data Interpretation, Statistical; D003666:Decontamination; D005260:Female; D005765:Gastrointestinal Agents / Q000627:therapeutic use; D006801:Humans; D006859:Hydrogen / Q000378:metabolism; D007037:Hypothyroidism / Q000382:microbiology*; D007421:Intestine, Small / Q000382:microbiology*; D008297:Male; D012294:Rifamycins / Q000627:therapeutic use; D000078262:Rifaximin; D013963:Thyroid Hormones / Q000097:blood
chemical_list: D000900:Anti-Bacterial Agents; D005765:Gastrointestinal Agents; D012294:Rifamycins; D013963:Thyroid Hormones; D006859:Hydrogen; D000078262:Rifaximin