Iodine Deficiency and the Brain

The effects of iodine deficiency on growth and development are known as the iodine deficiency disorders (IDDs). Most common is goitre at all ages, but most significant are the effects on brain development during pregnancy. The major effect of iodine deficiency is the clinical syndrome of endemic cretinism characterised in its fully developed form by mental defect, deaf mutism and spastic diplegia. This condition can be totally prevented by correction of the iodine deficiency before pregnancy. There is considerable variation in the degree of brain damage that occurs due to iodine deficiency in a given population. A meta-analysis of studies comparing iodine deficient populations with appropriate control groups reveals a mean loss of 13.5 IQ points. Experimental studies in the sheep, rat and marmoset confirm the effect of iodine deficiency on foetal brain development. They show that the effect is due to a slowing of neuroblast multiplication and differentiation and a consequent effect on neuroglial development. Iodine deficiency is now recognised as the most common cause of preventable brain damage in the world today. In 1990, the elimination of iodine deficiency as a cause of brain damage by the year 2000 was accepted by the UN system and substantial progress has been made since 1990 with the mass correction of iodine deficiency through Universal Salt Iodisation (USI).