Thyroid vertebrates. In fish, it is usually located below the gills and is not always divided into distinct lobes. However, in some teleosts, patches of thyroid tissue are found elsewhere in the body, associated with the kidneys, spleen, heart, or eyes. In tetrapods, the thyroid is always found somewhere in the neck region. In most tetrapod species, there are two paired thyroid glands – that is, the right and left lobes are not joined together. However, there is only ever a single thyroid gland in most mammals, and the shape found in humans is common to many other species. In larval
Computed tomography of the thyroid is required for patients less than 35 years old with nodules measuring more than 1 cm in the axial plane. The cutoff size for further evaluation is raised to 1.5 cm for patients more than 35 years old. This recommendation should be applied to the largest thyroid nodule in cases of multiple thyroid nodules. Incidentally discovered heterogeneous and enlarged thyroid glands should undergo dedicated ultrasound if the patient has no limited life expectancy or serious comorbidities. Primary thyroid carcinomas include papillary, follicular, medullary, and anaplastic carcinomas. Lymphoma and metastasis of other primary malignancies to the thyroid gland represent a minority