1, sick syndrome with normal thyroid function Some acute or chronic non-thyroidal diseases clinically show hypometabolism and low sympathetic response, such as fear of cold, weakness, swelling, poor appetite, constipation and other manifestations, and the measurement of low serum T3 and/or T4 is easily misdiagnosed as hypothyroidism. Low T3 alone is called low T3 syndrome, while severe cases can also show low T4, called low T4 syndrome. The decrease in serum T3 and T4 is a protective measure of the body, and the artificial addition of thyroid hormone preparations to increase the metabolic rate of the body will certainly aggravate the condition of the primary disease. 2, chronic nephritis Hypothyroid patients show pale skin, edema, anemia, hypertension and elevated blood cholesterol due to water and sodium retention. Patients with chronic renal insufficiency in nephritis often show abnormal thyroid hormone measurements, mainly a decrease in serum T3, but TSH is normal. In contrast, serum TSH is significantly elevated in patients with hypothyroidism. Anemia About 25-30% of hypothyroid patients show anemia, which is caused by various reasons. In primary hypothyroidism, the thyroid hormone is low and TSH is elevated, so the differential diagnosis is not difficult. 4. Plasma cavity effusion Plasma cavity effusion occurs in hypothyroidism due to slow lymphatic flow, increased capillary permeability, and secretion of highly hydrophilic mucin and mucopolysaccharide by lymphocytes, causing ascites, pericardial effusion, pleural effusion, and joint effusion. 5. Idiopathic edema Fibroblasts in hypothyroid patients secrete hyaluronic acid and mucopolysaccharide, which are hydrophilic and block lymphatic vessels, causing mucinous edema, mostly manifesting as non-concaveable edema, which is misdiagnosed as idiopathic edema. 6. Pituitary tumor Long-term hypothyroidism patients, especially pediatric patients, can show enlarged pituitary gland, which is sometimes misdiagnosed as pituitary tumor. Some female patients are misdiagnosed as pituitary prolactin-secreting tumor due to menstrual disorders and lactation, and laboratory tests reveal mild elevation of prolactin. Some hypothyroid patients are misdiagnosed as pituitary growth hormone-secreting tumor due to swelling of hands and feet, thick lips and large tongue, hoarseness, enlarged hands and feet, and enlarged pterygoid saddle.