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

Abstract

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.

Keywords

• Endemic goiter
• Iodine nutrition
• Hypo-and hyperthyroidism
• Thiocyanate
• Thyroid echogenicity/cytomorphology