DEFICIENCY
Causes of deficiency
Iodine occurs in the sea and soil as iodide. Sunlight releases elemental iodine, which is volatile. Although the iodine returns to the soil in rain, it is not completely replenished, and so the soil becomes steadily depleted – especially if flooding occurs as well, leaching it from the soil. Depletion is common in mountain areas subject to glaciation and heavy rainfall – including the Alps, Andes, Himalayas, and mountain regions of China. Also, the great plains of mid-west USA and central Africa have a lack. In Switzerland, goitre and cretinism were common; but after iodinised salt was introduced in 1922, goitre incidence fell dramatically and cretins were no longer born.
Endemic cretinism
Cretinism occurs when iodine intake by the mother is < 25 µg/day (normal intake is 100-150 µg/day). It is still prevalent in some parts of the world, affecting up to 10% of those living in I-deficient areas of India, Indonesia and China. However, it is easily prevented by iodine supplementation of the diet.
Cretinism is characterised by:
- mental deficiency
- deaf mutism
- spastic diplegia (cerebral palsy, both legs affected)
- reduced growth
Effects of reduced iodine intake in otherwise healthy people
Symptoms are mostly non-specific: (could apply to many other conditions)
Lethargy, weakness, cold-intolerance, apathy, poor concentration, angina pectoris, difficulty in breathing, oedema, constipation, irregular menstruation, muscle pain.
More specific signs: (more characteristic of deficiency)
Hoarseness, dry skin, reduced sweating, thin eyebrows, swollen eyelids, lowered pulse.
Iodine deficiency gradually leads to goitre.
World-wide problem
Iodine deficiency is a major world-wide problem. 1,5 billion people are at risk, i.e. 29% of the world’s population. 655 million have goitre. 20 million are mentally handicapped. (F. Delange, coordinator of the European office of the International Council for Control of Iodine Deficiency Disorders)
In Europe, 7 countries have goitre and iodine deficiency diseases under control: Norway, Sweden, Finland, Iceland, Austria, Switzerland, Denmark.
The situation in Norway
In 1934, 80% of schoolchildren had goitre. In 1977, the level was 1,5%. In iodine-poor regions, there is a higher risk of iodine deficiency, goitre and cretinism in households that are self-sufficient.