As per WHO guidelines, iodine deficiency disorders are endemic in the community when prevalence of goitre in school age children is more than -

Deficiency of Iodine The most obvious consequence of iodine deficiency is goitre but recent studies have indicated that there is a much wider spectrum of disorders, some of them so severe as to be disabling. They include : (a) hypothyroidism (b) retarded physical development and impaired mental function (c) increased rate of spontaneous aboion and stillbih (d) neurological cretinism, including deaf-mutism (e) myxoedematous cretinism, including dwarfism and severe mental retardation. To express this state of affairs more accurately, the term "endemic goitre", is now replaced by the term Iodine Deficiency Disorders (IDD) to refer to all the effects of iodine deficiency on human growth and development which can be prevented by correction of iodine deficiency. According to WHO, IDD is endemic in a community In which prevelence if goitre in a community is more than 5% Ref: Park 25th edition Pgno : 642