Guwahati thyroid epidemiology study: High prevalence of primary hypothyroidism among the adult population of Guwahati city

Background: Thyroid disorders have emerged as a common disease in India. Hence, it is pertinent to search the real reasons behind the high prevalence of thyroid disease in India, post salt iodization phase. Objective: This study was executed to unravel the nature of thyroid disorders and there associations with thyroid autoimmunity in the unexplored North east Indian region. Methods: This community based Cross sectional (pilot) survey involved 8 wards of Guwahati city, implementing the “cluster sampling technique”. Abnormal thyroid parameters were classified as Hypothyroid: serum T4 < 4.6 μg/dL and Thyroid stimulating hormone (TSH) > 4.2) μIU/mL; Subclinical hypothyroidism (SCH): normal serum T4 (4.6-12 μg/dL) and TSH > 4.2 IU/mL, and Anti-TPO antibody positive: titre of ≥ 34 IU/ml. Results: Out of the 209 subjects enrolled, incidence of newly detected SCH, self reported hypothyroidism, and cumulative figure of the hypothyroidism cohort were higher amongst female population (27.84%, 14.43%, and 42.27% respectively). Significant association was found between female sex and hypothyroidism [Relative risk (RR) 1.73 (1.16-2.56), P < 0.01]. Significant association was found between family history of thyroid disease and SCH (RR 2.59), elucidating a direct influence of heredity on pre-disposition towards thyroid disorder. Conclusion: A considerable percentage (33.01%) of the adult population in Guwahati city has some form of thyroid disorder. There is lack of evidence pointing out auto immunity being the major driver for primary hypothyroidism; hence we are left to reflect upon whether dietary iodine deficiency or being geographically located near to the sub-Himalayan goitrogenic belt, or frequent consumption of cyanogenic food stuffs, is cumulatively involved in thyroid disorder development.