ABSTRACT Objective Familial Mediterranean fever (FMF) is an autosomal recessive autoinflammatory disorder that is frequently seen in the eastern Mediterranean region. The thyroid gland can be affected in FMF patients through autoimmunity or amyloidosis. Here, we aimed to evaluate the structure and functions of the thyroid gland in addition to possible autoimmunity in FMF patients. Subjects and methods The study was conducted by the Endocrinology and Metabolism and Internal Medicine Departments. Thirty FMF patients and 30 age and gender-matched healthy controls were enrolled in the study. Free thyroxin (fT4), free triiodothyronine (fT3), thyroid-stimulating hormone (TSH), and anti-thyroid peroxidase (anti-TPO) autoantibodies were investigated. Detailed thyroid grayscale and Doppler Ultrasonography examinations and shear-wave elastosonography (SWE) were performed in the patient and control groups. Results Anti-TPO was detected in 24% (n = 7) of the patients. On the grayscale US, mean thyroid volumes were similar between the FMF and the control groups (p > 0.05). By Doppler US, thyroid vascularity observed was detected in 10.3% (n = 3) of the patients. SWE revealed that the mean velocity value of right vs. left lobe in the patient group was 1.77 ± 0.45 m/s and 1.95 ± 0.51 m/s, respectively. Compared to the control group, the mean velocity values were significantly higher in the right (p = 0.004) and left (p = 0.01) lobes of the patient group. The mean stiffness value in the patient group was also significantly higher in the right and left lobes [10.13 ± 5.65 kPa (p = 0.005) and 12.24 ± 6.17 kPa (p = 0.02), respectively]. Conclusion Recognizing the complications of FMF early in the course of the disease is as important as the early diagnosis of the disorder. Based on this, thyroid functions and changes in its structure should be evaluated carefully for early diagnosis of a possible coexisting thyroid disorder. Arch Endocrinol Metab. 2020;64(1):66-70