Low thyroid stimulating hormone in pregnancy test may be a physiological reaction during pregnancy or a manifestation of hyperthyroidism. 1. Physiological manifestations during pregnancy: During pregnancy, hormones in a woman’s body undergo large changes, especially human chorionic gonadotropin (HCG), progesterone, estrogen and other hormones will be significantly elevated. HCG is similar to thyroid stimulating hormone because of its alpha subunit, which has the effect of stimulating the thyroid gland. Some pregnant women may have low levels of thyroid stimulating hormone when they undergo a thyroid function test, which is a physiological reaction. 2. Hyperthyroidism: When hyperthyroidism occurs during pregnancy, low thyroid stimulating hormone may occur. At this time, it is necessary to improve the thyroid function test, thyroid ultrasound examination. If the pregnancy test found that the thyroid hormone is low, it is recommended to consult a doctor in time for further examination, to clarify the cause of the disease, and then follow the doctor’s instructions for treatment.