Thyroid nodules are a common clinical condition that can be caused by a variety of etiologies. All lumps in the thyroid gland are collectively referred to as thyroid nodules. There are three clinical types of thyroid nodules: hot nodules, cool nodules and warm nodules. The clinical significance of nodules varies with their size, number, location, texture and function. Therefore, it is of great clinical importance to correctly recognize the nature of thyroid nodules, especially to distinguish them as benign or malignant lesions. Differential diagnosis: 1. Hot nodules: The ability of the nodules to absorb iodine is greater than that of normal thyroid tissue. They are mostly benign autonomic functional thyroid adenomas. The secretion of thyroid hormone at the nodule inhibits the secretion of TSH, resulting in decreased absorption of 131I by the thyroid tissue outside the nodule. Therefore, the thyroid tissue around the nodule, or even the entire thyroid gland, does not absorb 131I. 2. Warm nodules: The intensity of radiation at the nodules is not different from that of other thyroid tissues. Most of them are benign tumors. Cold nodules: Thyroid adenoma: Most of them are solitary, slow growing and asymptomatic. The thyroid scan is warm nodules. If it is a toxic adenoma, it appears as a hot nodule. Adenomas can also bleed, necrotize and liquefy as cold nodules.