Clinical Nutrition

Lesson 8: Iodine deficiency disorders

Deficiency

The spectrum of Iodine Deficiency disorders (IDD) are seen in Table

Goiter, a swelling of the thyroid gland is the most obvious and common feature of iodine deficiency. (Figs 1, 2, 3). In iodine deficiency, the thyroid gland attempts to increase production of thyroid hormones. Hyperplasia of the thyroid cells occurs and thyroid gland increases in size. Goiter serves as a biological marker for the potential existence of other IDD.

Spectrum of Iodine Deficiency Disorders (IDD)

Fetus	Abortions Still births Congenital anomalies Increased perinatal mortality Increased infant mortality Neurological cretinism: mental deficiency, deaf mutism, spastic diplegia, squirts. Myxoedematous cretinism: mental deficiency dwarfism, hypothyroidism. Psychomotor defects
Neonate	Neonatal hypothyroidism
Child and adolescent	Retarded mental and physical development
Adult	Goiter and its complications Iodine induced hyperthyroidism
All ages	Goiter Hypothyroidism Impaired mental function Increased susceptibility to nuclear radiation.

During puberty and pregnancy, along with increased activity of estrogens, thyroxin activity also increases, thereby increasing the demand for iodine during these periods. Delayed onset of puberty and decreased fertility result due to iodine deficiency during these phases of life. The most damaging consequences of iodine deficiency are on fetal and infant development. Thyroid hormones and therefore iodine are essential for normal development of the brain and insufficient levels may lead to mental retardation of fetus or new born child. Endemic cretinism is the most severe effect of fetal iodine deficiency- cretins are mentally defective with physical abnormalities. In myxoedematous cretinism, hypothyroidism is present during fetal and early postnatal development and it leads to mental deficiency and stunted growth. In neurological cretinism, mental retardation along with hearing and speech defects and disorders of gait are present but hypothyroidism is absent. This syndrome is the result of low intake of iodine by a pregnant woman.

Iodine deficiency in school children has a effect on their mental performance. A difference of 13.5 points in IQ of iodine deficient and sufficient children has been found in studies conducted. This indicates the effect of iodine deficiency on neuropsychological development

Less severe iodine deficiency has been reported to cause elevated hearing thresholds in children.