There are many factors that can cause high thyroxine during pregnancy, usually due to abnormal changes in hormone levels in the body, the common causes are as follows: 1. 2, long time iodine deficiency, if a pregnant woman has a long time iodine deficiency or low iodine diet, it will cause insufficient intake of raw materials for thyroid hormone synthesis, thus causing a high level of thyrotropin. 3, mood swings, excessive stress, during pregnancy due to some changes in the pregnant women themselves caused by a lot of discomfort, discomfort is more intense or excessive mood swings, will also cause the level of thyroid hormone is increased. 4. Inadequate thyroid function can cause high levels of thyrotropin during pregnancy. 5, genetic factors, thyroid disorders and genetics sometimes have a certain relationship. 6, pregnant women during pregnancy, due to fetal growth and development and changes in body hormone levels after pregnancy, resulting in an increased demand for thyroid hormones. When the level of thyroid hormone becomes abnormal during pregnancy, it is recommended to go to a regular hospital for early treatment.