Association between hypothyroidism and small intestinal bacterial overgrowth.
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.
Lauritano
Ernesto Cristiano
EC
Internal Medicine Department, Catholic University of Sacred Heart, Gemelli Hospital, Largo A. Gemelli, 8, 00168 Rome, Italy.
Bilotta
Anna Lisa
AL
Gabrielli
Maurizio
M
Scarpellini
Emidio
E
Lupascu
Andrea
A
Laginestra
Antonio
A
Novi
Marialuisa
M
Sottili
Sandra
S
Serricchio
Michele
M
Cammarota
Giovanni
G
Gasbarrini
Giovanni
G
Pontecorvi
Alfredo
A
Gasbarrini
Antonio
A
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
D000900:Anti-Bacterial Agents; D005765:Gastrointestinal Agents; D012294:Rifamycins; D013963:Thyroid Hormones; D006859:Hydrogen; D000078262:Rifaximin