Hypothyroidism in pregnancy returns to normal thyroid function in some patients after delivery, but not in others. The most common cause of hypothyroidism during pregnancy is Hashimoto’s thyroiditis, but there are also other causes, such as iodine deficiency, hyperthyroidism after radioactive iodine 131 treatment, post-thyroidectomy, and pituitary or hypothalamic disorders. Hypothyroidism during pregnancy due to iodine deficiency is considered to be a cause of hypothyroidism, and after active treatment, the majority of the patients can return to a normal functional state of the thyroid gland after delivery. The use of levothyroxine sodium tablets during pregnancy in doses less than or equal to 50 μg is more likely to be discontinued after delivery. In cases of hypothyroidism in pregnancy due to other causes, or when the dose of levothyroxine sodium tablets is greater than 50 μg, it is less likely to be discontinued.