The biological importance of iodine is due to the fact that
it is essential for thyroid hormone production; the tragedy
of its deficiency lies in the easily preventable, but
largely irreversible, brain damage that occurs during fetal
growth and infant development. Endemic goitre is the most
visible manifestation of environmental iodine deficiency;
other, more severe, effects included retarded fetal brain
development, spontaneous abortion, stillbirths and infant
deaths. A deficiency of iodine later in infancy and
childhood causes mental retardation, delayed motor
development, growth failure and stunting, lethargy,
neuromuscular disorders (including squint and paralysis),
and speech and hearing defects. In 1993 at least 1572
million people worldwide were at risk of iodine deficiency
disorders (IDD), i.e. living in areas with goitre rates
above 5%. At least 655 million of this number are affected
by goitre, while an estimated 43 million people are affected
by some degree of IDD-related brain damage. To prevent IDD,
WHO recommends universal salt iodization. Iodized oil is the
preferred interim measure in areas of moderate or severe
deficiency that will not soon be covered by iodized salt.
IDD is known to be a significant public health problem in
118 countries. There has been progress recently. While only
46 had national salt-iodization programmes in 1990, their
number has increased in 1995 to 83.
Jim Akre, Nutrition unit, WHO, Geneva
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