Inadequate intake or metabolism of iodine .
It directly affects thyroid secretions, which influence heart action, nerve response, growth rate, and metabolism. Simple goitre , the most frequent result, is most common in areas without access to salt water and is rare along seacoasts. Severe, prolonged deficiency can cause hypothyroidism. Eating seafood regularly or using iodized table salt will prevent iodine deficiency. Some countries have made dietary iodine additives mandatory.