The Guidelines recommend the use of serum tumor markers for thyroid cancer diagnosis and treatment. China is a region with a high prevalence of thyroid nodules, with a prevalence rate of 18.6%, about 1 in 5 people, of which 5-15% of thyroid nodules can develop into malignant. Thyroid cancer has become a problem that cannot be ignored, and how to achieve early diagnosis and treatment of thyroid cancer, avoid post-operative recurrence, and improve the survival rate of patients has attracted extensive attention from the medical community. Recently, in the 2014 In Vitro Diagnostic Technology Summit Forum held in Chengdu, Professor Wu Yi, who was the deputy director of the Chinese Medical Association Oncology Society and the director of the Head and Neck Surgery Department of the Cancer Hospital of Fudan University, gave a speech on the topic of “Progress in the Diagnosis and Treatment of Thyroid Cancer”, sharing the current situation of thyroid cancer diagnosis and treatment with the participating national testing and clinical experts. He discussed the clinical value of serum tumor markers, mainly thyroglobulin (Tg) and calcitonin, for thyroid cancer, and demonstrated the significance of new in vitro diagnostic techniques for tumor management. The 2012 edition of the Guidelines for the Management of Thyroid Nodules and Differentiated Thyroid Cancer (hereinafter referred to as the Guidelines) recommends the introduction of serum tumor markers in the diagnosis and treatment of thyroid cancer. It is recommended that the introduction of serologic tumor markers in the diagnosis and treatment process can help clarify the type of thyroid cancer at an early stage and help doctors choose the correct treatment. In addition, follow-up monitoring through regular serological tumor marker tests is an important tool to determine the recurrence or metastasis of thyroid cancer. Iodine and thyroid stimulating hormone (TSH) are risk factors for thyroid cancer. Excessive or insufficient iodine intake can affect the structure and function of the thyroid gland and stimulate the development of thyroid cancer; long-term TSH stimulation can lead to thyroid hyperplasia, nodule formation and cancer. According to clinical staging, thyroid cancer mainly includes differentiated thyroid cancer (DTC, including papillary and follicular carcinoma), medullary thyroid carcinoma (MTC) and undifferentiated thyroid cancer. At present, the treatment of thyroid cancer is still mainly surgical, but the prognosis and the principles of surgical management of thyroid cancer differ accordingly depending on the pathological types. As one of the main references of the current guidelines related to thyroid cancer diagnosis and management in China, the American Thyroid Association (ATA) also affirms the significance of serum markers for thyroid cancer diagnosis and management in the third edition of the Guidelines for the Management of Thyroid Nodules and DTC – serum marker testing can better improve the sensitivity of adjuvant diagnosis. Among the serum markers related to thyroid cancer, Tg and Calcitonin have become important markers for postoperative monitoring of DTC and sensitive indicators for MTC screening, respectively, by virtue of their good specificity and sensitivity, and are receiving more and more attention in clinical practice. Clinical value of serum tumor markers Tg and Calcitonin More than 90% of thyroid cancers are DTC, which originates from thyroid follicular epithelial cells. most patients have a slow progression and nearly benign course, with a ten-year survival rate of more than 90% through standardized treatment. According to the Guidelines, patients with DTC are mainly treated with surgery and postoperative iodine 131 and TSH suppression, while their diagnosis and follow-up rely mainly on ultrasound and serum Tg to monitor the possibility of recurrence and metastasis by serum Tg levels, and they should be followed up for a long time. It is clinically proven that after total or near-total thyroidectomy and combined with radioactive iodine (RAI) therapy, the sensitivity and specificity of Tg detection is highest for determining DTC recurrence or residual after TSH stimulation (THS>30 mIU/L) and without the presence of Tg antibodies. In the absence of antibody presence, if Tg<0.5 ng/L after TSH stimulation, the probability that the patient is in a tumor-free survival state is 98%-99.5%. If Tg >2ng/L after TSH stimulation, especially if >10ng/L or persistently elevated, Tg is a highly sensitive indicator of persistent tumor presence. The Guideline recommends that after a patient’s postoperative review of serum TSH level reaches the standard, Tg and Tg antibody (TgAb) testing should be performed every 6-12 months during follow-up to keep serum Tg level below 2ng/ml. In the follow-up of DTC patients, Tg and TgAb tests must be performed by the same method, and patients should be re-evaluated if changes occur. The sensitivity of TgII is further improved compared to Tg, with a functional sensitivity of 0.09 ng/mL. The Elecsys® TgII test was officially approved by the CFDA in China on December 9, 2013. Calcitonin is an important tumor marker for MTC and correlates positively with tumor size. Normal human serum Calcitonin concentration should be less than 10ng/L. Serum Calcitonin levels in MTC patients are usually higher, often higher than 100ng/L. The degree of elevation correlates with tumor load and can be used as an MTC-specific tumor marker. For MTC screening, serum Calcitonin assay is more sensitive compared to ultrasound and fine needle aspiration (FNA), which is beneficial for early diagnosis. For diagnostic purposes, fine needle aspiration or Calcitonin testing can confirm and exclude patients with suspected MTC, and the presence of lymph node metastases and Calcitonin levels can help in the selection of clinical procedures. The European Consensus on the Management of Patients with Follicular Epithelial Differentiated Thyroid Cancer, published by the European Thyroid Association (ETA), recommends the use of Calcitonin for screening patients with thyroid nodules. Cases with elevated carcinoembryonic antigen (CEA) levels found on screening and PET-CT to exclude GI tumors are most likely to be MTC if Calcitonin levels are elevated. In the follow-up of MTC patients, basal Calcitonin and CEA testing can be performed and if the patient’s Calcitonin levels rise again after treatment, further testing is recommended to exclude recurrence If the patient’s Calcitonin level increases again after treatment, further testing is recommended to rule out recurrence. A study using the Elecsys® Calcitonin assay found significant increases in Calcitonin levels in samples from patients with MTC and relapsed MTC, which were significantly different from those of other patients with apparently healthy populations and thyroid nodules. Elecsys® Calcitonin was approved by the CFDA on March 28, 2014 and is now officially available in China. It is highly sensitive and can provide results even when only low levels of Calcitonin are present in the body, allowing for more reliable patient testing and follow-up.