Thyroid tissue has a strong ability to concentrate iodine and the thyroid gland requires a certain amount of iodine daily to produce physiologically active thyroxine. When iodine is deficient, the thyroid cells cannot synthesize enough thyroxine, which can lead to hypertrophy and hyperplasia of the thyroid gland. Depending on the nature of the goiter, it can be divided into diffuse goiter and nodular goiter. 1. In simple goiter, there are mostly no changes in thyroid function except for the enlargement of the thyroid gland and the resulting symptoms. The main symptoms are enlargement of the thyroid gland to varying degrees and compression of the surrounding organs by the enlarged nodules. In the early stages, the thyroid gland is diffusely enlarged, with a smooth, soft surface that moves up and down with swallowing. As the disease progresses, it may become nodularly enlarged. 2. Nodular goiter may have only one nodule in the early stage, but is usually multiple nodules. The nodule is soft or slightly hard, smooth and painless to the touch. The disease develops slowly and most of them are asymptomatic. The clinical characteristics of goiter in general are that there are no symptoms other than enlargement of the thyroid gland in the early stage, and some patients may experience compression of adjacent organs and tissues in the later stage.