Thyroid nodules are not necessarily hypothyroidism. The diagnosis of hypothyroidism is based on thyroid hormone levels. Thyroid nodules refer to lumps within the thyroid gland that are morphologically abnormal. The occurrence of thyroid nodules may be related to factors such as genetics, radiation, and abnormal iodine intake, and are mainly detected by ultrasound. Hypothyroidism refers to abnormal functioning of the thyroid gland, a disease caused by decreased secretion and synthesis of thyroid hormones. Thyroid nodules and hypothyroidism are not a single disease, nor do they necessarily have a causal relationship, but the two diseases can co-exist. For example, patients with Hashimoto’s thyroiditis may have both thyroid nodules and hypothyroidism. Patients diagnosed with thyroid nodules or hypothyroidism need to follow the doctor’s instructions for treatment and have regular checkups.