The normal range of thyrotropic hormone is 0.35-5.5 µIU/mL, and the reference value of different hospitals may be slightly different. 0.005 µIU/mL suggests that the patient’s thyrotropic hormone is too low, which may be due to hypopituitarism, hyperthyroidism, etc., and it should be diagnosed with the combination of the thyroid function and the imaging examination. 1. Hypopituitarism: thyrotropin is secreted by the pituitary gland. Hypopituitarism caused by pituitary tumors, craniocerebral injuries, and ischemic necrosis of the pituitary gland will lead to a decrease in the synthesis and release of thyrotropin, which will reduce the level of thyrotropin in the serum. 2. Hyperthyroidism or subclinical hyperthyroidism: Excessive thyroid hormones in the blood circulation will inhibit the release of thyrotropin, resulting in lower thyrotropin levels. Patients with abnormal thyroid stimulating hormone values are advised to go to the hospital promptly.