Thyroid Autoimmune Disorders Among Reproductive-Age Women In An Iodine-Sufficient Region Of North-East India

Abstract

Background: Autoimmune thyroid disorders are common among women and may adversely affect health during the reproductive years. Although iodine deficiency remains an important cause of thyroid dysfunction, thyroid autoimmunity can persist in populations with adequate iodine intake. Thyroid peroxidase (anti-TPO) and thyroglobulin (anti-Tg) antibodies are established biomarkers of autoimmune thyroid disease. North-East India has historically experienced endemic goitre, and persistent thyroid dysfunction following universal salt iodization may partly reflect underlying thyroid autoimmunity.

Objective: To estimate the prevalence of thyroid autoantibody positivity and examine its association with thyroid biochemical function among women of reproductive age in an iodine-sufficient region of North-East India.

Methods: A community-based cross-sectional study was conducted among women of reproductive age in Imphal East district, Manipur. The analysis included 242 women with available measurements of thyroid-stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), anti-TPO and anti-Tg antibodies. Participants were categorized according to antibody status. Continuous variables were summarized using mean ± standard deviation or median with interquartile range, as appropriate. Associations between antibody status and thyroid function were assessed using the Mann–Whitney U and chi-square tests. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated, with p<0.05 considered statistically significant.

Results: Among the 242 participants, 110 (45.5%) were anti-TPO positive and 102 (42.1%) were anti-Tg positive. Overall, 119 women (49.2%; 95% CI: 42.7–55.7%) had at least one positive thyroid autoantibody, while 93 (38.4%) were positive for both antibodies. The median concentrations of TSH, FT4 and FT3 were 1.83, 1.36 and 2.46, respectively. Women with at least one positive antibody had significantly higher median TSH than antibody-negative women (3.11 vs. 1.56; p=0.0046). At an exploratory TSH threshold of >4.0, elevated TSH was observed in 42.9% of antibody-positive women compared with 14.6% of antibody-negative women (OR=4.38; 95% CI: 2.36–8.12; p<0.001).

Conclusion: Thyroid autoantibody positivity was highly prevalent, affecting approximately half of the women studied. Antibody-positive women had significantly higher TSH levels and a markedly greater likelihood of elevated TSH, indicating a potential role of thyroid autoimmunity in thyroid dysfunction despite adequate iodine nutrition. Further large-scale community studies incorporating urinary iodine assessment, dietary factors, thyroid ultrasonography and reproductive characteristics are needed to identify determinants and establish the clinical significance of this substantial burden of thyroid autoimmunity.