Thyroid ultrasonography, thyroid hormones and urine iodine excretion levels in patients with inflammatory bowel disease

Aim: Inflammatory bowel disease (IBD) is a group of diseases with an increase in worldwide prevalence, characterized by chronic inflammation in gastrointestinal tract with relapses and remissions, also considered as a systemic disease due to its extraintestinal involvements. IBD, although it is not clear, is considered to have an autoimmune pattern in its pathogenesis and mainly consisted of ulcerative colitis (UC) and Crohn's disease (CD). The coexistence of IBD with autoimmune thyroid disease and thyroid hormone disorders is expressed by other studies yet a certain coherence couldn't be stated. The iodine which is essential for the production of thyroid hormones, is obtained by food intake and is shown to be more deficient than normal population in conditions which cause malabsorption such as IBD. In this study we examined thyroid hormones, thyroid antibodies and urine iodine excretion in patients diagnosed with IBD. We also examined thyroid morphology and characteristics including thyroid nodule properties in IBD patients. Materials and Methods: In this study, IBD patients who were referred to Gastroenterology policlinics and were admitted in Gastroenterology wards of Ankara City Hospital, and control group of healthy adults applying for routine control to Endocrinology policlinics were examined between May 2019 and October 2019. Pregnant patients, patients younger than 18 years old and older than 65 years old, patients with chronic diseases, patients with known thyroid disorders that required medication, intake of any drugs in the last 6 months that could affect thyroid metabolism and iodinated contrast uptake in the recent year were not included in the study. Demographic features, clinical and pathologic data, thyroid stimulating hormone (TSH), free triiodithyronine (fT3), free thyroxin (fT4), anti thyroid peroxidase (anti-TPO), anti thyroglobuline (anti-Tg), urinary iodine excretion levels and thyroid ultrasound properties were recorded in each group. C-reactive protein (CRP), erythrocyte sedimentation rate, hemoglobine (Hb), and ferritine is also analyzed in IBD group and recorded along with their physical examination notes in order to calculate their disease activity. Results: The study consisted of 31 UC, 30 CD and 31 healthy control group. Age and gender distribution between the groups were similar. The disease acitivity in UC according to mayo score system was found 1 in mean (min:0, max:7), whereas according to Truelove and Witts' %77.4 patients were considered mild, %19.4 were moderate and %3.2 were found to have severe activity. Crohn disease activity index (CDAI) was found 88.5 in mean (min:29, max:283) in patients with CD. No statistical significance was found between IBD patients with sedimentation, CRP, Hb and iron deficiency anemia (p=0.384). TSH, fT3, fT4 were found similar between groups. Only one patient was diagnosed with hypothyroidism in UC group whereas all patients in CD and control groups were euthyroid but not found statistically significant. Mean anti-TPO levels were found higher than controls in patients with UC and CD (respectively p=0.043ve p=0.001). Anti-TPO was found positive in %16.7 of CD and %3.2 of UC patients whereas there were none in the control group. Due to this finding positive anti-TPO was significantly higher than the control group (p=0,019). Mean anti-Tg levels were similar in UC and CD patients and also higher than found in the control group (respectively p=0.022 ve p=0.004). Mean urine iodine excretion found in UC group was 91.6 ug/L, in CD group 86 ug/L and in the control group 89 ug/L with no statistical significance (p=0.943). İodine deficiency rate was also similar between the groups and detected in %61 of the patients in all groups (p=0.999). According to the thyroid ultrasonography examination in IBD and control patients, mean thyroid volume and color flow doppler patern showed no statistical significance between any of the groups. However significant difference in parenchymal heterogenity was observed (p=0.021). Thyroid parenchyma was found severely heterogenous in 7 patients(%22.6) with UC, 9 patients with CD (%30), whereas none found in the control group. Thyroid nodules were detected in 12 patients with UC (38.7%) in a total number of 26, in 14 patients with CD (46.7%) in a total number of 14 and in 10 patients in control group(%32.3) had 14 nodules as total. There were no significance found between the groups in presence, number and the location of the nodules (p=0.714). Also the structure, echogenity, margin irregularity, border regularity and peripheral halo presence in the nodules were found similar between the groups (respectively p=0.686, p=0.617, p=0.361, p=0.665, p=0.626 ve p=0.356). Age, gender and disease involvement type was not found relatable to the disease activity in UC and CD. Similarly thyroid volume assessed with ultrasonography, parenchymal heterogenity, thyroid blood flow pattern and disease activity was not found significant. Mean CDAI was found lower in the CD patients which thyroid nodules were detected than CD patients without nodules (65 and 138.5; p=0.048),and a negative correlation was found between CDAI and nodule number (r =-0,408; p=0,042). Conclusion: Inflammatory bowel disease is characterized by chronic inflammation in gastrointestinal tract, causing malabsorption and also a systemic disease with its extraintestinal involvements. UC and CD are often related with autoimmune diseases but thyroid diseases are yet considered as an extraintestinal involvement of the IBD. In this study we detected no significal difference in thyroid hormones between IBD patients with mild to moderate disease acitivity and control group. We also stated that autoimmune thyroid disease indicators such as anti-TPO and anti-Tg were higher in the IBD group than the control group being more evident especially in CD. Because of causes such as disruption in the gut flora, causing protein losing enteropathy and helper T lymphocyte (Th1) / cytotoxic T lymphocyte (Th2) mediated immunity dominance, autoimmune thyroid diseases can be said to accompany IBD especially CD. According to this, thyroid functions and antibodies should be assessed periodically in IBD patients especially in CD and iodine intake should be questioned and nutrition suggestions should be given to those individuals. To elaborate the relationship between IBD and thyroid diseases and evaluate the impact of IBD disease activity on this issue, more extensive studies should be conducted about thyroid dysfunctions and thyroid morphology in larger populations. Key words: Inflammatory bowel disease, autoimmune thyroid diseases, urine iodine excretion, thyroid ultrasonography