The thyroid gland is large on one side and small on the other. 2. The most common thyroid diseases include thyroid tumors, thyroid nodules, thyroid cysts, Hashimoto’s thyroiditis or acute and chronic thyroiditis, all of which may lead to goiter or thyroid atrophy. Therefore, with the above analysis, one side of the thyroid gland is large and the other side is small, so you should immediately go to the endocrinology department of the hospital for relevant examinations, including thyroid function tests and thyroid ultrasound.