Serum thyroid stimulating hormone is a hormone secreted by the pituitary gland, and its main function is to promote thyroid hormone secretion by the thyroid gland. The amount of thyroid stimulating hormone needs to be related to the type of disease the patient is suffering from. For example, in patients with hyperthyroidism, the TSH is higher than normal if the hyperthyroidism is caused by a central cause. If the hyperthyroidism is caused by a disease such as Graves’ disease, the TSH is less than normal. The value of TSH in the presence of hypothyroidism is related to the cause, for example, TSH is below the normal range in central hypothyroidism, while it is above the normal range in hypothyroidism caused by Hashimoto’s thyroiditis, iodine deficiency, etc.