This is a multinodular goiter of the thyroid gland, the most common cause for enlargement of the thyroid. Multinodular goiters are usually derived from simple diffuse goiters over many years. Goiters may be caused by iodine deficiency, ingestion of a goitrogen, or a defect in thyroid hormone biosynthetic pathway, but in most cases the cause is not known. Whatever the cause for impaired thyroid hormone synthesis, the follicular epithelium adapts by becoming more sensitive to normal levels of TSH, with resultant increase in thyroid size and cellular activity to overcome the mild impairment. Thus, most patients are euthyroid, as in this case, with normal levels of thyroxine, and are bothered only by local discomfort or cosmetic deformity of the enarlged gland in the anterior neck region. A Hashimoto thyroiditis could appear similar to this in the early stage, with painless enlargement, but the thyroid would be pale, not as nodular, and more symmetric.