The weakness of legs half a month after iodine 131 treatment for hyperthyroidism may be related to malnutrition, hypothyroidism and other reasons, it is recommended to consult a doctor in time. 1. Malnutrition: If the patient is weak and malnourished after iodine 131 treatment, the symptoms of tenderness of legs may appear, and the symptoms can be gradually improved by supplementing nutrition. 2. Hypothyroidism: after iodine 131 treatment, if the patient’s drug dose is too much, it may cause hypothyroidism, and then the patient may have the symptom of soft legs. Iodine 131 treatment for hyperthyroidism is more obvious, it is recommended to go to the endocrinology department of the hospital in a timely manner to improve the auxiliary examination, to clarify the cause of the cause of the disease, and then treat the cause.