Thyroid carcinoma is the common endocrine system malignant neoplasm. At present it has become the malignant neoplasm of fastest growing incidence rate. More than 90% thyroid carcinoma is thyroid differentiated carcinoma（DTC）. Postoperative oral L-thyroxine suppressing thyroid stimulating hormone (TSH) treatment is the standard therapy in DTC patients. While TSH-suppressive therapy with L-thyroxine can cause subclinical hyperthyroidism in treatment of patients with thyroid differentiated carcinoma. The impact of this therapy on cognitive functions and mood have not been systematically studied. The investigators infer the subclinical hyperthyroidism caused by TSH-suppressive therapy may impact cognitive function and mood disorders in DTC patients. The aim of this study is to explore the possible mechanism of cognitive function impairment in the course of TSH-suppressive therapy by rat model of total thyroidectomy + TSH-suppressive therapy and clinical trials. The result of this study may provide clinical and experimental basis for the side effects risk result form TSH-suppressive therapy in DTC patients.

1. Object:

   Patients aged 18-65 years; newly diagnosed differentiated thyroid carcinoma and undergone thyroidectomy according to the China thyroid association guidelines for the Management of thyroid nodule and thyroid cancer; followed by TSH-suppressive therapy 6 /12 months.

2. Clinical information, examination data and neuropsychological assessments:

Information is obtained from medical record abstraction. Serum T3, T4, FT3, FT4, TSH, TG-ab, TPO-ab, TG levels and neuropsychological assessments are examined after TSH-suppressive therapy 6 /12 months. Cognitive complaints were assessed with the Mini-Mental State Examination (MMSE), Clock Drawing Test (CDT), Digit Symbol test (DST), Wechsler Memory Scale (WMS), Aphasia Battery of Chinese （ABC） and patient health questionnaire-9 (PHQ-9).

Healthy volunteers (normal T3, T4, FT3, FT4, TSH, TG-ab, TPO-ab, TG) are recruited to match the patients with age, gender, education level, etc.

Inclusion Criteria:

• Newly diagnosed differentiated thyroid carcinoma.
• Undergo thyroidectomy according to the China thyroid association guidelines for the Management of thyroid nodule and thyroid cancer.
• Followed by TSH-suppressive therapy 6 /12 months.

Exclusion Criteria:

• Current or past disorder/disease of the central nervous system or medical condition impacting cognitive functioning.
• Head trauma history with prolonged loss of consciousness.
• Epilepsy, dementia, or learning disability.
• Current or past psychotic-spectrum disorder or current major affective disorder.
• Current substance abuse/dependence.
• Daily tobacco and alcohol use.
• Whole brain irradiation or surgery.
• Prior cancer diagnosis or chemotherapy treatment.
• Active autoimmune disorder.
• Insulin-dependent diabetes.
• Uncontrolled allergic condition or asthma.
• Chronic use of oral steroid medication.
• Hormone therapy (estrogen, progestin compounds).

Patients aged 18-65 years; newly diagnosed differentiated thyroid carcinoma and undergone thyroidectomy according to the China thyroid association guidelines for the Management of thyroid nodule and thyroid cancer; followed by TSH-suppressive therapy 6 /12 months.