Clinical features SAT is mostly seen in young and middle-aged women aged 30 to 50 years, 3 to 6 times more than men. The onset of the disease is seasonal, with its peak in winter and spring. Patients often have symptoms of upper respiratory tract infection, such as fever, accompanied by fear of cold, chills, fatigue and lack of appetite. The characteristic symptoms are pain and pressure in the thyroid gland, often radiating to the submandibular area, behind the ear, or in the neck, and worsening when chewing and swallowing. Thyroid lesions may start in one lobe and later expand or move to another lobe, or remain confined to one lobe. The lesion is enlarged and hard, with significant pressure pain. In typical cases, the entire disease phase can be divided into acute phase with hyperthyroidism, remission phase with hypothyroidism (transitional and hypothyroid phases), and recovery phase (normal thyroid function). In mild or atypical cases, the thyroid gland is only slightly enlarged, with mild pain and tenderness, no fever, mild systemic symptoms, and may not be clinically hyperthyroid or hypothyroid. In typical cases, thyrotoxicosis usually lasts 3 to 6 weeks and hypothyroidism can last from several weeks to six months. The duration of the disease varies and can last from several weeks to more than six months, usually 2 to 3 months, hence the name SAT. after remission, there is a possibility of relapse. Diagnostic criteria ①. Enlarged, painful, hard and tender thyroid gland, often with signs and symptoms of upper respiratory tract infection: fever, malaise, lack of appetite, enlarged lymph nodes in the neck, etc. (ii) Accelerated erythrocyte sedimentation rate. (iii) Transient hyperthyroidism. ④Inhibited 131I uptake rate. ⑤Thyroid autoantibodies thyroid microsomal antibodies, thyroglobulin antibodies are negative or low titer. ⑥Thyroid puncture or biopsy with multinucleated giant cells or granulomatous changes. SAT can be diagnosed when 4 of the above 6 criteria are met. Diagnosis is based on clinical presentation. Most patients have a history of upper respiratory tract infection 1 to 3 weeks prior to onset of the disease. Most patients have fever (37.5 to 39.5°C), malaise, lack of appetite, and poor mental health. Physical examination reveals a mild to moderate enlargement of the thyroid gland, which may appear as nodules with a moderately hard texture and significant tenderness, and pain may appear simultaneously or sequentially in both lobes of the thyroid gland. Systemic symptoms similar to hyperthyroidism may occur early in the course of the disease, due to the transient release of thyroxine into the blood after thyroiditis. Laboratory tests ①Blood picture shows normal or slightly low red blood cell count, normal or high white blood cells and neutrophils. Serum protein electrophoresis shows a decrease in albumin, while alpha and beta globulins are often increased. The basal metabolic rate may increase to 30%-50% in the early stage of the disease and decrease to below -20% in the later stage of the disease. The erythrocyte sedimentation rate is often significantly increased (>50 mm/h, even up to 100 mm/h). Typical laboratory findings include 131I uptake rate and serum triiodothyronine (T3) and four-triiodothyronine (T4) levels showing a “separation phenomenon”, i.e., early in the course of the disease As the disease progresses, the 131I uptake rate gradually increases, while the serum T3 and T4 levels gradually decrease. If the lesion is small, the patient’s iodine metabolism may not be abnormal, but isotope scans reveal a significant decrease in the 131I uptake capacity of the lesion, and serum protein-bound iodine and T4 and T3 values are often increased. When the entire thyroid gland is involved, the image of the entire cervical radiological background is significantly elevated, and the thyroid image is extremely unclear, or even non-visible. If the lesion involves only one part of the thyroid gland, a clinically irregularly bounded mass can be palpated. The external imaging of the thyroid gland can be seen as a radiolucent area equivalent to the mass, the so-called “cold nodules”, which disappear after appropriate treatment. The ultrasound sonogram of the B-mode Doppler SAT is characterized by pseudocystic manifestations or hypoechoic lesions, with inhomogeneous echogenicity within the thyroid gland and gradual decrease of inhomogeneous hypoechogenicity from the outside to the inside. Color Doppler flow imaging shows an increase in blood flow signal around the hypoechoic area and very little inside. After thyroid function is normalized, the ultrasound image returns to normal. When the affected thyroid gland is mildly enlarged, the lesion is nodular and hypoechoic, either single or multiple nodules, with an irregular shape that appears to be oblong, with clear boundaries between the normal thyroid tissue, no envelope, sparse internal echogenicity, basically uniform echogenic distribution, and approximately no echogenicity, with a few lesions with strong echogenic spots but no acoustic shadow, and no significant changes in the posterior wall or posterior aspect. The right side of the thyroid gland is slightly more commonly invaded, but the thyroid gland can be invaded bilaterally. The CT scan focuses on the demarcation between the lesion and the extra-glandular structures rather than on the margins of the deep nodules within the gland, and the integrity of the margins of the thyroid gland on the side of the lesion and the clarity of the surrounding fatty spaces are important indicators of benignity and malignancy. Magnetic resonance imaging of the normal thyroid shows a homogeneous T1-weighted signal intensity slightly greater than that of the skeletal muscle, and in T2-weighted sequences, the normal thyroid shows a high signal compared to the cervical muscle. Fine needle aspiration biopsy: Fine needle aspiration cytology is feasible for definitive diagnosis in cases of goiter or nodules in the thyroid gland. Ultrasound-guided puncture of the suspected area can further increase the positive diagnostic rate. Pathological changes: Typical pathological changes are: granulomatous infiltration of histiocytes in the gland and the presence of foreign body giant cells and even pseudotuberculous nodules with mild to moderate fibrosis, which are characterized by uneven distribution of lesions and lesions similar to tuberculous nodules, hence the names granulomatous thyroiditis, giant cell thyroiditis and tuberculous thyroiditis.