Bilobar thyroid follicular cysts are associated with long-term iodine deficiency, embryonic developmental abnormalities, and thyroid adenomas. 1. Long-term iodine deficiency: it is a common cause of thyroid cysts. Long-term iodine deficiency will induce nodular goiter, and some of the nodules will develop into cysts. 2. Abnormal embryonic development: Abnormal development of thyroglossal ducts and remnants of the fourth gill slit during the embryonic stage of development can lead to the development of cysts after birth. 3. Thyroid adenomas: Cysts can also develop when thyroid adenomas undergo degenerative changes and old hemorrhages. In addition, some bilobar follicular cysts of the thyroid gland may start out as small cysts. The presence of these factors suggests prompt medical attention to determine the cause of the condition and, if necessary, cooperation with the doctor.