İt is known that there is a relationship between some diseases and blood groups. The objective of our study is to investigate how often ABO and Rh blood groups are seen in benign thyroid diseases, especially in autoimmune-mediated thyroid diseases, and hence whether there is an association between blood groups and thyroid diseases. A total of 958 patients who were followed due to any benign thyroid disease were included in the study. The study population comprised 958 patients, 550 with Hashimoto's hypothyroidism, 160 with non-Hashimoto's hypothyroidism, 103 with iatrogenic hypothyroidism, 93 with central hypothyroidism, and 28 with Graves' and 24 with non-Graves' hyperthyroidism. Of the patients, 47.1% belonged to the O blood group, 30% to the A blood group, 15.2% to the B blood group, and 7.7% to the AB blood group while 90% were Rh-positive. The ratio of those with the O blood group was determined to be significantly higher in the Hashimoto's hypothyroidism group compared to the other disease groups. In the non-Hashimoto's hypothyroidism group, however, the ratio of the AB blood group was statistically significantly higher. While autoimmune diseases were more common in those with the O blood group, they were significantly lower in the AB blood group (p < 0.001). In our study, we determined that the ratio of the O blood group was significantly higher among patients with hypothyroidism due to Hashimoto's thyroiditis. These findings imply that there might be a relation between O blood group and Hashimoto's thyroiditis.
Keywords: ABO; Blood groups; Hashimoto; Thyroid.