If it is a malignant, functional solid thyroid nodule, it is generally more serious. If it is a benign, non-functional solid thyroid nodule, it is generally more mild. Whether a solid thyroid nodule is serious or not depends mainly on the nature of this nodule; if it is a benign thyroid nodule, it is usually not serious. If it is a malignant thyroid nodule, which is also known as thyroid cancer, it is more serious, and thyroid cancer requires surgery. Secondly, to determine whether a thyroid nodule is serious, it also depends on whether the nodule has a function. If it is a high-functioning thyroid nodule, also known as a high-functioning adenoma, which secretes thyroid hormones and causes the patient to develop hyperthyroidism, this condition is also more serious and requires surgery. Thyroid nodules are a relatively common thyroid disorder, and the nodules can be solid or cystic. Generally, cystic thyroid nodules are benign, while solid thyroid nodules can be benign or malignant. The nature of the nodules can be determined by ultrasound and biopsy. If the thyroid nodule is benign and there are no symptoms of pressure, it can be observed and reviewed regularly. If there are symptoms of pressure, or if the nodule is malignant, surgery is needed.