Introduction: Autoimmune thyroid disease is a multifactorial disorder, which has been linked to the exposure of certain environmental factors.
Aims and Objectives: To investigate whether thyroid autoimmunity (TAI) is significantly associated with identifiable and potentially modifiable environmental factors in Maltese individuals.
Materials and Methods: A case-control observational study was conducted among 324 Maltese patients, who had been screened for TAI within the previous 12 months. 164 cases (positive thyroid peroxidase [TPO-Ab] and/or thyroid stimulating hormone receptor antibodies [TSH-R Ab]) and 160 controls (negative antibodies) were recruited. A questionnaire sought information on drug history, social/reproductive history, stress and iodine intake, while blood specimens were collected to measure glycosylated haemoglobin, thyroid function, TPO-/TSH-R Ab status, 25-hydroxyvitamin D level and hepatitis C antibody status. A stool sample was collected for Helicobacter pylori.
Results: Both TPO-Ab and TSH-R Ab positive individuals were exposed to a higher amount of smoking pack years (P=0.038 and 0.037 respectively). No significant predictors of TSH-R Ab positivity were identified on multivariate regression analysis. The odds for TPO-Ab positivity was increased by female gender (OR 2.815 [95% CI, 1.387, 5.714]; P=0.004) and discontinuation of smoking (OR 2.367 [95% CI, 1.213, 4.621]; P=0.012), while birth in winter (OR 0.470 [95% CI, 0.253, 0.871]; P=0.017) and higher intake of iodine rich foods (OR 0.864 [95% CI, 0.761, 0.981]; P=0.024) decreased the odds for TPO-Ab development.
Conclusion: TPO-Ab positivity appears to be affected by environmental factors in Maltese individuals, though not all are potentially modifiable.