A thick neck requires vigilance for endemic goiter, a geographically related thyroid disorder caused mainly by insufficient dietary iodine content. Endemic goiter is an iodine deficiency disease that occurs primarily in areas where the iodine content of the soil is low to the point of insufficient iodine availability through food and water, and occurs when iodized salt is not provided. Iodine deficiency causes an increase in the size and number of thyroid epithelial cells, resulting in an enlarged gland and no other abnormal physical findings, a condition known as simple or endemic goiter. This deficiency is more common in women than in men and is more common during puberty and pregnancy. Consumption of iodized salt is the most common treatment for this condition. Some natural sources of iodine, such as marine foods (fish, crabs, etc.) and green vegetables grown in marine soil can also provide sufficient amounts of iodine in the body. Due to the wide spread of iodized salt consumption in our country, it has played an excellent role in the prevention and control of endemic goiter, which is now rare. Therefore, the presence of a thick neck still requires an examination to determine whether the neck diameter is thickened due to an enlarged thyroid gland. Therefore, in order to be cautious, it is best to go to the hospital for an ultrasound examination to measure the volume of the thyroid gland to clearly determine the disease when thickening of the neck occurs.