The thick tendons on both sides of the neck may be a physiological phenomenon caused by excessive fitness, but also need to consider the jugular vein varicose, hyperthyroidism and other disease factors. 1. Physiological phenomenon: when the patient often fitness activities, exercise neck muscles, may make the neck muscles become thick, the appearance of the neck on both sides of the thick, at this time belongs to the physiological thickening, generally does not cause adverse effects. 2. Disease factors: (1) Jugular vein varicose: when the patient suffers from heart disease, such as right heart failure, right ventricular infarction, etc., it may make the jugular vein reflux obstruction, jugular vein blood filling, resulting in jugular vein varicose, which leads to the patient’s neck on both sides of the tendons become thick. (2) Hyperthyroidism: When the thyroid gland is hyperfunctional, the patient will secrete too much thyroid hormone, resulting in excessive synthesis of thyroid hormone and resulting in goiter. The thyroid gland is located in the superficial tissues of the neck, so the sides of the neck will become large after goiter. The causes of enlarged tendons on both sides of the neck are different, so it is recommended to go to the hospital in time for examination, to clarify the specific causes of the disease and then follow the doctor’s instructions for treatment.