Hypoechoic thyroid nodule means that the nodule echoes are lower than the surrounding thyroid parenchyma, and is a manifestation of thyroid nodules under ultrasound examination. Hypoechoic or very hypoechoic thyroid nodules are generally considered to be a suspected malignant ultrasound feature and may be a bad sign, but they also need to be evaluated in conjunction with the size, morphology, blood flow, and echogenicity of the thyroid nodule. If malignancy of a thyroid nodule is suspected, a puncture biopsy may be needed to clarify the nature of the nodule. If hypoechoicity is used as a diagnostic criterion, the diagnosis is more sensitive and less specific; if very hypoechoicity is used as a diagnostic criterion, the diagnosis is less sensitive and more specific. Thyroid nodules are detected and should be treated under the supervision of a doctor.