Iodine Deficiency Disorders (IDD) are a spectrum of clinical conditions resulting from inadequate iodine intake leading to impaired production of thyroid hormones:

• Triiodothyronine (T3)

• Thyroxine (T4)

These hormones regulate:

• Basal metabolic rate

• Protein synthesis

• Growth and skeletal maturation

• Brain development (especially fetal & early childhood)

• Lipid and cholesterol metabolism

• Conversion of carotene to Vitamin A

Because the brain depends on thyroid hormones during fetal life and the first 2–3 years of life, iodine deficiency is the leading preventable cause of intellectual disability worldwide.

2. Pathophysiology

When iodine intake is insufficient:

1. ↓ Iodine → ↓ T3/T4 production

2. Pituitary releases ↑ TSH

3. Thyroid gland hypertrophy → Goitre

4. Chronic deficiency → impaired neuronal migration & myelination

5. Irreversible brain damage in fetus/infant

3. Spectrum of Iodine Deficiency Disorders

4. Clinical Manifestations

A. Goitre

Enlargement of thyroid gland due to chronic TSH stimulation.

Grades:

B. Hypothyroidism

• Dry skin

• Cold intolerance

• Weight gain

• Puffy face

• Constipation

• Fatigue

• Bradycardia

• Slow reflexes

C. Hyperthyroid Features (Occasionally after iodine supplementation)

• Exophthalmos

• Tachycardia

• Weight loss

• Tremor

D. Cretinism (Severe Congenital Deficiency)

Two forms:

Neurological cretinism

• Severe intellectual disability

• Deaf-mutism

• Squint

• Spasticity

Myxedematous cretinism

• Dwarfism

• Puffy face

• Thick tongue

• Severe hypothyroidism

5. Risk Factors

Dietary

• Living in iodine-poor soil regions (highlands, flood plains)

• Lack of iodized salt

• Cassava-based diet (goitrogens)

• Millet, cabbage, cauliflower excess intake

Physiological

• Pregnancy

• Lactation

• Rapid growth (childhood, adolescence)

Socioeconomic

• Poverty

• Poor nutrition education

• Limited access to fortified foods

6. Signs and Symptoms

7. Diagnostic Criteria

Diagnosis may be clinical or biochemical:

Population indicators (WHO)

Individual diagnosis

• Goitre

• Hypothyroidism

• Developmental delay in iodine-deficient region

8. Investigations

9. Management

Goals

1. Restore iodine levels

2. Prevent brain damage

3. Correct thyroid dysfunction

4. Prevent recurrence

A. Non-Pharmacological Management

Dietary Measures

Use iodine-rich foods:

Universal salt iodization is the most effective global strategy.

B. Pharmacological Treatment

1. Iodized Oil Therapy

Used in endemic areas when iodized salt unavailable.

2. Lugol’s Solution

• 3 drops (~21 mg iodine) single dose

3. Hypothyroidism Treatment (if present)

• Levothyroxine replacement (lifelong in congenital cases)

10. Monitoring

11. Complications

• Permanent intellectual disability

• Deaf-mutism

• Growth failure

• Pregnancy loss

• Infertility

12. Prevention

Public Health Measures

• Universal salt iodization

• Monitoring salt iodine content

• Maternal supplementation programs

• Neonatal screening

Individual Measures

• Use iodized salt daily

• Avoid washing salt before cooking

• Add salt after cooking (iodine heat-sensitive)

13. Prognosis