Describe the iodine deficiency disorders and their control.

Iodine Deficiency Disorders

• Iodine is required for the synthesis of thyroid hormone, which governs fetal and infant brain development
• The spectrum of disorders by life stage:
• Fetus — abortion, stillbirth, congenital anomaly, increased perinatal mortality, and cretinism
• Neonate — neonatal goitre and neonatal hypothyroidism
• Child and adolescent — goitre, hypothyroidism, impaired mental function, retarded physical development, and poor school performance
• Adult — goitre with its complications, hypothyroidism, impaired mental function, and iodine-induced hyperthyroidism
• Cretinism occurs in two forms — neurological, the commoner, with severe intellectual disability, deaf-mutism, squint and spastic diplegia, but a euthyroid state and normal stature; and myxoedematous, with hypothyroidism, severe growth retardation and dwarfism
• The most important public health point is that the bulk of the damage is not goitre or cretinism but a subtle, widespread reduction in the intellectual capacity of an entire population
• A shift of several IQ points across a whole population, invisible in any individual, has enormous cumulative consequences for education and productivity — and it is entirely preventable at negligible cost
• Iodine deficiency is described as the world’S commonest preventable cause of intellectual disability
• The damage is irreversible once it has occurred, which is why prevention must reach the woman before and during pregnancy, not the child afterwards
• Epidemiology in INDIA — classically the sub-Himalayan goitre belt stretching from Kashmir to the north-east, where iodine has been leached from the soil by glaciation, flooding and heavy rainfall
• But surveys have shown deficiency in nearly every state and district, including coastal ones, so NO area can be assumed safe — which is precisely the argument for a universal rather than a targeted programme
• Goitrogens contribute — substances in cabbage, cauliflower, mustard, soyabean, cassava and tapioca, which interfere with iodine utilisation; they matter chiefly where iodine intake is already marginal
• Assessment of a community — goitre prevalence in school-age children by palpation, graded 0, 1 and 2; urinary iodine concentration, which is the best indicator of current intake, with a median of 100 to 199 micrograms per litre indicating adequacy; neonatal TSH screening; and salt iodine content at household and retail level
• Note the different time-frames — goitre reflects past deficiency and takes years to regress, while urinary iodine reflects intake over the last few days, so goitre prevalence is a poor way to judge a recent programme
• Prevention — universal salt iodisation is the strategy, chosen because salt is consumed by everyone, in a fairly constant amount irrespective of income, is centrally produced, and iodisation is cheap
• The Indian standards — not less than 30 parts per million at production and 15 ppm at the consumer level, the difference allowing for loss in transit
• Practical points for storage and use — iodine is lost by exposure to heat, light, moisture and long storage, so salt should be kept in a closed container away from the fire, and added to food after cooking rather than during it
• Monitoring is by the spot testing kit at field level and titration for confirmation
• The national iodine deficiency disorders control programme conducts surveys, monitoring, laboratory support and health education
• A caution worth stating — iodisation can precipitate iodine-induced hyperthyroidism in older people with long-standing nodular goitre; this is transient and greatly outweighed by the benefits, but it is a genuine effect and should be acknowledged rather than denied
• The damage is to the brain, not the neck; goitre is merely the visible sign of a far larger problem
• Population-wide IQ loss is the real cost, invisible in any individual and entirely preventable
• Store salt closed and away from the fire, and add it after cooking rather than during
• Judge a programme by urinary iodine, since goitre reflects past deficiency and takes years to regress
• No area can be assumed safe, which is the argument for universal rather than targeted iodisation
• Damage is irreversible once done, so prevention must reach the woman before and during pregnancy
• Neurological cretinism is euthyroid with normal stature, unlike the myxoedematous form
• Thirty parts per million at production and fifteen at the consumer, the difference allowing for transit loss
• Salt was chosen because everyone eats it in a fairly constant amount regardless of income
• Goitrogens matter where iodine is marginal, and include cabbage, cassava, mustard and soyabean
• Acknowledge iodine-induced hyperthyroidism honestly; it is real, transient and greatly outweighed by the benefit
• Spot testing kits allow field monitoring, with titration reserved for confirmation