Thiocyanate in excess develops goiter followed by auto immune thyroid diseases even after effective salt iodization in a rural community of north east India.

PURPOSE: Salt iodization in Manipur of north-east India failed to prevent endemic goiter, therefore an in depth study carried out to evaluate thyroid functions of goitrous subjects in a randomly selected region.

METHODS

Goiter survey conducted in children and women of reproductive ages by palpation followed by measurement of urinary iodine, thiocyanate and house-hold salt iodine to evaluate iodine nutritional status and consumption pattern of bamboo-shoots (BS). In all grade-2 goitrous subjects, free thyroxine, triiodothyronine, TSH, TPO and Tg antibodies, thyroid volume and echogenecity by ultrasonography and cytomorphology of thyroid by FNAC studied.

RESULTS

Study population was 2486 children and 1506 women, goiter prevalence was 12.59% and 16.27% respectively; median urinary iodine and mean thiocyanate were 166 µg/l and 0.729 ± 0.408 mg/dl while salt iodine was ≥30 ppm. Serum thyroid hormones and TSH profiles of all grade-2 goitrous subjects showed 16.21% were subclinically hypothyroid, 2.16% overt hypothyroid, 4.86% subclinically hyperthyroid and 6.48% overt hyperthyroid, serum TPO- and Tg-antibodies found positive in 41.62%. Ultrasonographic results showed 24% had enlarged thyroid and 86.4% hypoechoic. Cytomorphological studies showed prevalence of colloid goiter (41.08%), lymphocytic thyroiditis (37.83%), Hashimoto's thyroiditis (8.10%), autoimmune thyroiditis (4.32%), sub-acute thyroiditis (2.16%) and 1.62% each papillary, medullary carcinoma, simple diffused hyperplasia and adenomoid nodular goiter.

CONCLUSIONS

Grade-2 goitrous individuals in this mild goiter endemic region were affected by hypo- and hyperthyroidism with hypoechoic thyroid and thyroiditis. Thiocyanate that originates from BS even in presence of adequate iodine developed goiter and led goitrous population towards such diseases.