**1. Introduction**

Goiter is the enlargement of the thyroid gland which can be due to a variety of conditions. Nodular goiter is one of the most common endocrine disorders affecting the thyroid gland. It is endemic to certain populations and regions especially those with iodine deficiency. It also tends to occur with a higher frequency in women and in the fourth to fifth decades of life [1]. The prevalence of goiter is variable worldwide and is correlated with iodine intake of regional populations. In approximately 3600 B.C., Chinese medical writings were the first to show a decrease in size of goiter after ingestion of seaweed and burnt sea sponge, and they continued to remain as effective remedies for goiter worldwide as was documented in the writings of Hippocrates, Galen, Roger, and Arnold [2].

After initiation of iodine prophylaxis programs in over 2100 school girls in the United States in 1917 by David Marine and colleagues, iodized salt was introduced in the United States in 1922 for prevention of endemic goiter. Later in 1930 iodized salt became widely available in the United States [3]. The salt iodization is a good approach for decreasing iodine deficiency in population, as it is a universal foodstuff, inexpensive, and easily available and intake is relatively consistent [4]. Approximately 120 countries, including the UK, Canada, Brazil, China, India, Thailand, and Singapore, have adopted mandatory iodization of all food-grade salt [5]. Currently the WHO recommends daily intake of 150 mcg iodine for adults,

250 mcg for pregnant and lactating women, and 90 mcg for children <2 years of age that can be easily obtained by iodized salt, processed food, and milk products [6]. Prevalence of goiter still remains 4–7% in the United States even after iodine supplementation [7].

Goiter can be classified as solitary or multiple, diffuse or nodular, and toxic or nontoxic on an anatomical and functional basis. The nontoxic goiter is due to abnormalities of iodine supplies or metabolism without any abnormal thyroid function. In children goiter tends to be smaller and diffuse, whereas in older people they are usually large and nodular.
