Iodine deficiency disorders and fluorosis
IDD is the range of harm from too little iodine, from goitre to cretinism. Fluorosis is harm from too much fluoride in water, damaging teeth and bones.
The IDD spectrum by stage of life
| Stage | Disorders |
|---|---|
| Fetus | Abortion, stillbirth, birth defects, cretinism: neurological (deaf-mutism, squint, spastic legs, mental retardation) or myxoedematous (dwarfism, hypothyroidism) |
| Newborn | Neonatal goitre, neonatal hypothyroidism, more infant deaths |
| Child and adolescent | Goitre, lower IQ and poor school performance, slow physical growth |
| Adult | Goitre and its complications, hypothyroidism, lower work output, iodine-induced hyperthyroidism when iodine intake rises suddenly |
Causes and prevention of IDD
- Cause: soil and water poor in iodine (Himalayan belt, flood plains, hilly areas where rain washes iodine away), so local foods are poor in iodine.
- Goitrogens add to it: thiocyanates in cabbage, cauliflower and cassava (tapioca) block iodine uptake by the thyroid.
- Need: WHO advises about 150 µg iodine a day for adults and 250 µg a day in pregnancy and lactation.
- Universal salt iodisation is the main measure: the sale of non-iodised salt for direct human use is banned.
- Monitoring: urinary iodine (a population median below 100 µg/L means deficiency), goitre surveys in school children, and salt-testing kits used in the community.
- Storage: keep iodised salt in a closed container away from heat and damp.
- Programme: National Goitre Control Programme (NGCP) 1962, renamed the National Iodine Deficiency Disorders Control Programme (NIDDCP) in 1992.
- Global IDD Prevention Day is 21 October.
Fluorosis: types
| Type | Cause | Features |
|---|---|---|
| Dental fluorosis | Fluoride above 1.5 mg/L while the teeth are forming in childhood | Chalky white patches, then yellow-brown stains and pits (mottled enamel); permanent |
| Skeletal fluorosis | Years of drinking water high in fluoride (usually above 3 mg/L) | Pain and stiffness of the back, neck and joints, bent spine, calcified ligaments; crippling in severe cases |
| Genu valgum (non-skeletal form) | High fluoride with a poor diet; reported where jowar is the staple in parts of Andhra Pradesh and Telangana | Knock-knees, muscle weakness, stomach complaints |
Prevention of fluorosis
- Give endemic villages a safe water source (surface or piped water).
- Defluoridation: the Nalgonda technique (developed by NEERI; uses alum and lime) at home or village level, or activated alumina filters.
- A diet rich in calcium, vitamin C and antioxidants (milk, curd, green leafy vegetables, amla) lowers the harm.
- Avoid extra fluoride: black rock salt, very strong tea, and fluoride toothpaste for young children in endemic areas.
- Test water sources and survey school children for mottled teeth.
- Endemic areas include parts of Rajasthan, Gujarat, Andhra Pradesh, Telangana, Karnataka and Tamil Nadu (for example Dharmapuri and Krishnagiri). A national programme for prevention and control of fluorosis supports testing and treatment.
IDD vs fluorosis
Iodine and fluorine are both halogens, and both problems follow geography: the disease is found where the soil or water is.
On home visits, a community nutritionist tests household salt with a salt-testing kit. In fluoride-belt villages she helps the panchayat arrange safe drinking water and teaches families to add milk, curd and greens to their meals.
2 marks: “What is the iodine content prescribed for iodised salt?” At least 30 ppm at the production level and at least 15 ppm at the consumer level.
5 marks: “Write a short note on fluorosis.” Cause (fluoride in water above 1.5 mg/L); dental, skeletal and genu valgum forms; endemic states; prevention (safe water, Nalgonda technique, calcium and vitamin C).
10 marks: “Explain the spectrum of iodine deficiency disorders and the measures to prevent them.” Define IDD (Hetzel); life-stage table; causes and goitrogens; indicators (goitre rate, urinary iodine); universal salt iodisation and monitoring; NGCP 1962 renamed NIDDCP 1992.
Iodine too little → goitre and brain; fluoride too much → teeth and bones. Salt fixes the first; safe water fixes the second.