With the increasing incidence of thyroid cancer year by year, as well as advances in high-frequency ultrasound and physicians’ attention to thyroid cancer, the detection rate of early thyroid cancer is increasing year by year. About 90% of thyroid cancers are of the differentiated type, and the vast majority of these in turn require only radical surgery to be done well and post-operative treatment with only levothyroxine tablets, including treatment of thyroid cancer and replacement therapy, without the need for chemotherapy, radiation and other special treatments. Patients with thyroid cancer have a high quality of life and do not lose their workforce, especially since the vast majority are clinically curable, and simply and less accurately, but very practically, the vast majority of differentiated thyroid cancers pose little risk to life itself. Among all solid malignancies, differentiated thyroid cancer has the best prognosis. This is the fact that thyroid cancer patients need to know, so as to avoid unnecessary questions such as “I have cancer, I won’t live long”, “My doctor said I don’t want chemotherapy, radiotherapy and other special treatments, is it that I am hopeless …… “This will lead to a high degree of “mental tension” among patients! In recent years, due to the rapid development of nuclear medicine, iodine 131 and other nuclear treatment methods are widely used in medical examination and treatment process, which has brought a good promotion effect, and iodine 131 treatment after thyroid cancer surgery is also getting more and more attention from physicians and patients. However, the current situation is that, on the one hand, some physicians and patients do not pay enough attention to thyroid cancer, or they have the stereotype of “talking about nuclear”, which makes some high-risk thyroid cancer patients miss the treatment of iodine 131. On the other hand, some physicians or nuclear medicine experts, as well as some patients and their families, are too pessimistic about the prognosis of most differentiated thyroid cancers and believe that since thyroid cancer is a thyroid cancer, nuclear therapy should be administered. In other words, there is a suspicion of “over-treatment”. Clinically, we often come across early-stage thyroid cancer and thyroid cancer with low risk of recurrence, who, after receiving iodine 131 nuclear therapy, have serious adverse reactions, which are similar to severe premenopausal syndrome, such as weakness, poor performance, edema of the lower limbs, reduced or even absent sexual function, slow response, etc.. The combination of Chinese and Western methods of treatment for a long time also fails to relieve the symptoms. Therefore, when treating thyroid cancer with iodine 131, especially differentiated thyroid cancer, the risk of postoperative recurrence of thyroid cancer and the possible advantages and disadvantages of nuclear therapy should be fully evaluated, so as to avoid “over-treatment” which is not done when treatment is needed, but not done when it is not needed! The following is a brief introduction from 5 aspects. Iodine 131 therapy should be considered in the following cases: 1. distant metastases such as lung and bone; 2. tumor breaks through the true perithelium of thyroid; 3. tumor does not break through the perithelium, but there are lymph node metastases, poor pathological subtypes of papillary carcinoma (high cell, columnar cell, diffuse sclerosis, etc.), multiple cancer foci, vascular invasion, non-papillary carcinoma (follicular, low differentiation). 4. Other conditions that are assessed as high risk of recurrence and metastasis after surgery. Note: For those who are older than 45 years old and whether the tumor diameter exceeds 2cm or 3cm, whether these cases must be treated with iodine 131 therapy needs to be combined with clinical risk assessment, and cannot be used as indications for iodine 131 therapy across the board. The timing of starting iodine 131 therapy after surgery: Iodine 131 therapy can be performed after the wound heals and after avoiding iodine-rich foods (such as seaweed, seaweed, sea fish and other seafood) and stopping taking thyroxine tablets for one month. During this period, it is not advisable to perform enhanced CT examinations and not to eat iodized salt. Preparatory measures needed before treatment: Since iodine-containing foods and thyroid hormones have an effect on the uptake of iodine 131 by the thyroid gland, the use of thyroid hormones and iodine-containing foods and drugs should generally be stopped for more than 4 weeks before treatment. In addition, before taking iodine-131 treatment, blood should be drawn to check thyroid function, thyroglobulin (Tg) and globulin antibody (TgAb) and routine blood tests, ultrasound of the neck, plus chest X-ray or CT scan of the chest if necessary. However, enhanced CT examination is not done – because the enhancement agent contains iodine, which affects the treatment effect. Fourth, pay attention to the protective isolation after iodine 131 treatment: Iodine 131 treatment requires a certain period of protective isolation, after all, it is a nuclide, the impact, even if small, but ultimately the impact. It is reported in the literature that “the public should be exposed to only one case of thyroid cancer patient treated with iodine 131 within one year” on the premise that the following points can be achieved: 1) sleep in separate beds within 12 days; 2) maintain a distance of more than 1 meter from family members within 3 days (assuming 6 hours of exposure per day); 3) go to work after 5 days (assuming a distance of more than 1 meter from colleagues and 8 hours of exposure per day). more than 1 meter distance between you and your colleagues (assuming 8 hours of contact per day). It is recommended to extend the above time. However, iodine 131 for medical use is a short half-life nuclide, which means that it is metabolized very quickly and after 1 month there is no 131 iodine in the body and normal activities can be carried out. Also after taking iodine-131, after urinating and defecating for the first 1 week, flush the bathroom with water more often because a lot of iodine-131 will be discharged from urine and faeces during this time, and irradiate your family. Also, after iodine-131 treatment, it is better to avoid contact with children for one month, especially infants and children. V. Possible side effects after iodine 131 treatment are: Iodine 131 treatment is generally safe and differs greatly from radiation therapy and chemotherapy for other tumors, with different nature and consequences. Other radiotherapy methods are only for the patient himself, and even if there are side effects, they are only for the patient himself, and do not pose any potential harm to others; however, iodine 131 may pose potential harm to others, so it is not advisable to have frequent contact with family members or others for 1 week before treatment, especially to stay away from infants and children. After receiving radioactive iodine 131 treatment, there is generally only slight gastrointestinal discomfort and swelling and pain in the neck, while a few cases cause serious toxic side effects such as vomiting, hair loss, bone marrow suppression and gonadal suppression; it is rare to cause increased infertility and other secondary tumors. The overall incidence is very low and should be noted.