Radioactive iodine 131 treatment does not affect male fertility. During radioactive iodine 131 treatment, beta rays will be released, which can make part of the thyroid follicle epithelium degenerate and necrotic, reduce the synthesis and secretion of thyroid hormone, and thus achieve the purpose of treating hyperthyroidism. The distribution of iodine 131 in tissues other than the thyroid gland is small and the residence time is short, and the effect on the reproductive system is also small, so there is no effect on the fertility of male patients in general. It is important to note that this treatment is not recommended for women who are pregnant. Men undergoing radioactive iodine 131 treatment can consult their doctors if they need to prepare for pregnancy.