Tumefaction in the neck. The most visible symptom of thyroid problems is tumefaction in the neck. The reason of this tumefaction is goiter, which means that thyroid is inflamed. Goiter is possible equally in both cases – due to hypothyroidism and hyperthyroidism. However, tumefaction in the neck may be caused by other reasons additionally. Thereby, any kind of neck shape changings or deformations must undergo medical investigation in the early stages.