ENDEMIC INFANTILE HYPOTHYROIDISM IN A SEVERE ENDEMIC GOITRE AREA OF CENTRAL AFRICA

Thyroid function and exposure to dietary goitrogenic factors (iodine deficiency and thiocyanate overload) were studied at birth and from birth to 7 years in 200 neonates and 347 children living in the severe endemic goiter area of Ubangi Northern Zaire. Serum T4 was at the lower limit of normal at birth (104 +or- 4 nmol/1) and stayed at that level during the 1st year of life (123 +or- 9) (NS) but decreased to 75 +or- 8 (P0.001) at 2-4 years and to 62 +or- 6 (P.001) at 5-7 years of age. Mean serum FT4 decreased from 10.4 +or- 0.9 pmol/1 during the 1st year to 8.2 +or- 1.0 (NS) at 2-4 years (NS) and to 7.7 +or- 0.9 (P0.05) at 5-7 years. Mean serum TSH was 10.4 (8.4-12.9) mU/1 (geometric mean +or- 1 SEM) during the 1st year 10.1 (7.5-13.7) (NS) at 2-4 years and 24.3 (18.5-31.9) (P0.05) at 5-7 years. Mean serum T3 was 3.23 +or- 0.12 nmol/1 during the 1st year and remained stable thereafter. The frequencies of low T4 (T477 nmol/1) high TSH TSH (TSH50 mU/1) and low T4 and T3 (T31.69 nmol/1) were twice as high at 5-7 years as in the 1st year 65% 42% and 15% respectively). The urinary iodide concentration of the children was stable and low throughout the study period. By contrast serum thiocyanate concentration which was high at birth (129 +or- 5 cmol/1) decreased to normal values between 3-12 months of age and increased again during and after weaning (1-3 years of age) to reach a value of 138 umol/1 which was comparable to that observed in adults in the same area. Thiocyanate concentration was high (133 +or- 7 umol/1) in the mothers serum but low in the mothers milk (57 +or- 3 umol/1) (P0.001). Multivariate analysis showed that both iodine deficiency and thiocyanate overload were explanatory factors of the serum levels of T4 FT4 and TSH in children. The results show that infantile hypothyroidism is more frequent at 5-7 years of age than at birth or during the 1st year of life. The deterioration in thyroid function during and after weaning is linked to persistent iodine deficiency accompanied by an increase in thiocyanate overload. Variability in age at onset severity and duration of infantile hypothyroidism might explain the wide range of psychomotor and physical abnormalities observed in a lage proportion of subject in this area. (authors modified)