A goitre may be classified either as nodular or diffuse. Nodular goitres are either of one nodule (uninodular) or of multiple nodules (multinodular).
Uninodular goitre: one thyroid nodule; can be either inactive, or active (toxic) – autonomously producing thyroid hormone.
Multinodular goitre: multiple nodules; can likewise be inactive or toxic, the latter is called toxic multinodular goitre and associated with hyperthyroidism. These nodules grow up at varying rates and secrete thyroid hormone autonomously, thereby suppressing TSH-dependent growth and function in the rest of gland. Inactive nodules in the same goitre can be malignant.Thyroid cancer is identified in 13.7% of the patients operated for multinodular goitre.
Diffuse goitre: the whole thyroid appearing to be enlarged due to hyperplasia.
Class I: the goitre in normal posture of the head cannot be seen; it is only found by palpation.
Class II: the goitre is palpable and can be easily seen.
Class III: the goitre is very large and is retrosternal (partially or totally lying below the sternum), pressure results in compression marks.