Iodine is one of the 14 essential trace elements in the human body, and the establishment of the national policy of universal salt iodization (USI) in China at the end of the 20th century has improved the mental retardation and even intellectual disability of a large number of newborns in iodine-deficient areas caused by insufficient iodine nutrition. Is the more iodine supplementation the better? According to some provincial and municipal epidemic prevention departments and scientific research units, they found that the incidence of goiter not only did not decrease after salt iodization, but also increased year by year, and some of the findings also showed that excessive iodine loading, like iodine deficiency, can also cause retarded brain development and brain dysfunction. Therefore, the health effects of excess iodine loading are of increasing concern. It has also been reported in the literature that thyroid damage from excess iodine includes: (1) hyper-iodothyroidism; (2) hyper-iodothyroidism; (3) autoimmune diseases such as Choban’s thyroiditis and Graves’ disease; and (4) hyper-iodothyroid papillary carcinoma. It is believed that the mechanism of goiter caused by high iodine is similar to that of low iodine in that high iodine inhibits the synthesis of thyroxine, resulting in a decrease in T 4 in the blood, which in turn stimulates the secretion of thyroid stimulating hormone (TSH) and increases the size of the thyroid tissue. This results in the accumulation of colloid in the thyroid follicles, causing them to dilate and become enlarged. It has also been reported that high iodine levels can induce apoptosis in thyroid cells, and excessive apoptosis of thyroid cells will inevitably cause damage to thyroid structure and function. Similarly, high iodine levels can cause apoptosis of brain cells, which inevitably causes damage to the central nervous system, thereby affecting learning, memory and intelligence. According to the results of the survey, the incidence of thyroid disorders tends to increase significantly in the 5 years after USI, with the highest rate of thyroid nodules, followed by hyperthyroidism, thyroid adenoma and hypothyroidism. Among them, hypothyroidism has the worst prognosis and causes the most harm. For newborns, hypothyroidism can cause cretinism, mental retardation, and growth retardation; for adults, it can lead to reduced comprehension and memory, serious mental disorders, xerosis, and dementia; for other organs, it can lead to bradycardia, heart enlargement, myocardial damage, arteriosclerosis, and angina pectoris. It will directly affect people’s quality of life and will cause great losses to families and society. In outpatient clinics, the necessary biochemical screening is one of the means of early detection of thyroid disorders for those who are thin, fat, have mucinous edema without a cause, have arrhythmias such as rapid heart rate, bradycardia, atrial fibrillation, etc. Special attention should be paid to women over 40 years old. In order to improve the health and quality of life of our staff, early diagnosis of thyroid disease is the main primary prevention measure; early treatment of those who already suffer from thyroid disease to prevent complications and hypothyroidism; early detection of thyroid tumors and timely surgical treatment are important secondary and tertiary prevention measures. Therefore, during the screening of thyroid diseases, palpation, ultrasound, and timely biochemical examination are carried out simultaneously to facilitate early diagnosis and make it less likely to be missed or misdiagnosed. At the same time, health education for patients with thyroid disease, USI monitoring and the selection of non-iodized salt for thyroid disease caused by high iodine are sometimes necessary measures.