Small intestinal bacterial overgrowth (SIBO), similarly as thyroid diseases, is characterized by chronic diarrhea or constipation, but it is not known whether there is a causal relationship between these disorders.
Aim: The aim of the study was to assess thyroid function indices in different clinical forms of SIBO.
Materials and methods: The study was performed in 34 patients with diarrhea predominant SIBO (group I), 30 with constipation predominant SIBO (group II) and 30 clinically healthy subjects (control group - K). Small intestinal bacterial overgrowth was assessed with lactulose hydrogen breath test (LHBT) using the breath-hydrogen analyzer (Gastrolyser, Bedfont). Serum thyrotropin (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) levels were determined by immunochemical method (ELFA) and anti-thyroid peroxidase (ATPO) protein level by immunoenzymatic method (ELISA).
Results: LHBT value was respectively in groups: K - 8,5 ± 2,9 ppm, I - 66,9 ± 16,9 ppm, II- 62,0 ± 15,5 ppm (p <0,001). The levels of hormones were similar in group K and I, whereas in group II differentiated: FSH 2,5 ± 0,7 vs. 3,8 ± 1,8 mU/L (p <0,05), FT3- 5,1 ± 1,2 vs. 3,7 ± 1,0 mU/L (p <0,05), FT4 - 14,1 ± 2,5 vs. 9,4 mU/L (p <0,01). In both groups of patients the levels of ATPO were statistically significantly higher than in the control group - respectively: K - 6,3 ± 3,1 IU/ml , I - 39,9 ± 23,4 IU/ml (p < 0,001), II - 94,1 ± 56,3 IU/ml (p <0,001).
Conclusions: Thyroid function may be impaired in patients with small intestinal bacterial overgrowth which should be taken into account in the diagnostic and therapeutic management of the diseases of these organs.
Keywords: small intestinal bacterial overgrowth; thyroid hormones; thyroid peroxidase.