Thyroid cysts currently have no definitive cause identified. Previously, most believed they were possibly related to iodine deficiency, as such deficiency leads to thyroid hyperplasia and an increase in thyroid cysts. However, it was later discovered that in some high-iodine coastal areas, the incidence of thyroid cysts remains high. This suggests that variations in iodine levels, such as switches from low to high iodine or from high to low iodine, can also lead to the occurrence of thyroid cysts. Additionally, it is currently believed that there might be some connection with radiation and the use of mobile phones and computers, but there is no definitive conclusion. Regardless, once thyroid cysts occur, it is important on one hand to eliminate the possibility of malignant features, ruling out thyroid cancer, and on the other hand to ensure thorough thyroid function tests to understand if there are any abnormalities in function and whether treatment is needed.