Hypothyroidism causes mucus edema of the vocal cords, so it can cause changes in the voice. Hypothyroidism is caused by a low concentration of thyroid hormones in the blood. Thyroid hormones are important hormones that affect the processes of material and energy metabolism in the body and promote human growth and development. When the secretion of thyroid hormones decreases for various reasons, that is, when hypothyroidism occurs, it causes the body to develop mucinous edema. Typical hypothyroidism is characterized by fear of cold, little or no sweating, puffiness of the face and eyelids, poor nausea, weight gain, memory loss, unresponsiveness, and other hypometabolic symptoms. Mucinous edema is a typical symptom of hypothyroidism. Mucinous edema in hypothyroidism can also involve the vocal cords, resulting in mucinous edema of the vocal cords, making the patient’s voice thicker and slower. Therefore, hypothyroidism can cause voice changes.