Dysgenesis of thyroid is the common type of childhood hypothyroidism in environmentally iodine deficient areas of north India.

Forty-five children (28 girls and 17 boys; mean age 4.5 years) with hypothyroidism referred to us from January 1989 to November 1990 were evaluated prospectively for the pattern of hypothyroidism by hormone assays, scintiscan and urinary iodine estimation. Among the 6 children from non-endemic areas, athyreosis and/or hypoplasia were seen in 3, ectopia in 2 and dyshormonogenesis in 1. Of 39 children from moderate to severe environmentally iodine deficient regions, 18 (46%) had athyreosis and/or hypoplasia and 10 (26%) ectopic thyroid. Iodine deficiency was seen in 4, dyshormonogenesis in 4, secondary/tertiary hypothyroidism in 2 and thyroiditis in 1. The mean age of these children at the onset of symptoms was 1.4 years and at clinical presentation 4.5 years. There was significant growth retardation with 54% of children being below the 5th centile of Indian standards. There was no significant difference in the age at onset of symptoms and presentation, clinical features and bone age for the different types. The levels of serum total T4 were significantly low in dysgenesis (athyreosis, hypoplasia and ectopia, p < 0.001). Dysgenesis of the thyroid is the most common type of childhood hypothyroidism in iodine deficiency endemias. We postulate that severe iodine deficiency in the intrauterine and early neonatal period may lead to dysgenesis of the thyroid.