Thyroid nodules form as a result of overgrowth of normal thyroid tissue. The etiology of the condition is not yet fully understood and may be related to inflammatory stimuli and iodine intake. Thyroid nodules are one or more clusters of abnormal tissue structure within the thyroid gland confirmed by imaging, and are scattered lesions caused by abnormal local growth of thyroid cells. Various thyroid disorders such as thyroid hyperplasia, inflammation, and tumors may manifest as thyroid nodules. Most of the thyroid nodules are diagnosed by thyroid ultrasound and are mostly benign with a small percentage of malignant nodules. Several factors have been clearly and strongly associated with the prevalence of thyroid nodules, such as inflammatory stimuli, gender, age and iodized salt intake and ionizing radiation. Recent studies have reported that metabolic disorders and overweight/obesity are also associated with the development of thyroid nodules. The presence of thyroid nodules is recommended to visit the hospital for prompt treatment.