Abstract
ObjectiveThyroid peroxidase antibody (TPOAb), the most common antibody frequently measured in population surveys is a protein expressed in the thyroid gland. We conducted the present study to analyze the prevalence and incidence of thyroid auto immunity and natural course of TPOAb in a population based study.Material and MethodsThis prospective study was conducted within the framework of the Tehran Thyroid Study (TTS) on 5783 (2376 men and 3407 women) individuals aged ≥ 20 years who had thyroid function tests at baseline and were followed up for median 9.1 year with TPOAb measurements at approximately every 3 years.ResultsThe mean age of total population at baseline was 40.04±14.32. At baseline, of the 5783 participants, 742 (12.8%) were TPOAb positive, with higher prevalence among women than in men (16.0 vs. 8.5%, p = 0.001). The prevalence of TPOAb positivity in the total population was 11.9, 14.9 and 13.6% in the young, middle age and elderly respectively. The total incidence rate (95%CI) of TPOAb positivity in the total population (5020) was 7.1 (6.36–7.98) per 1000 person-years of follow-up, with higher incidence of TPOAb positivity among young participants, i.e. 8.5 (7.5–9.7) per 1000 person-years. Sex specific incidence rate demonstrated that TPOAb positivity was higher in women, 9.3 (8.2–10.7) per 1000 person-years. The Cox's proportional hazard model analysis showed that the hazard ratio of developing TPOAb positivity was higher in women than men (P<0.0001) and tended to increase slightly with serum TSH levels (P<0.0001) but declined with increasing age (P<0.0001) in the total population. Our findings demonstrate that individuals, who became TPOAb positive in each phase, had significant elevation of TSH levels at the phase of seroconversion, compared to baseline values.ConclusionGender, age and elevated serum TSH were found to be risk factors for developing TPOAb positivity. Furthermore, compared to baseline a significant elevation of TSH levels during seroconversion phase was observed in TPOAb positive individuals.
Highlights
Autoimmune thyroid disorders (ATDs) are the commonest autoimmune endocrine diseases, characterized by the frequent presence of auto antibodies directed against thyroglobulin (Tg), thyroperoxidase (TPO) and thyrotropin receptor (TRAB)[1,2]
Sex specific incidence rate demonstrated that Thyroid peroxidase antibody (TPOAb) positivity was higher in women, 9.3 (8.2–10.7) per 1000 person-years
Compared to baseline a significant elevation of thyroid stimulating hormone (TSH) levels during seroconversion phase was observed in TPOAb positive individuals
Summary
Autoimmune thyroid disorders (ATDs) are the commonest autoimmune endocrine diseases, characterized by the frequent presence of auto antibodies directed against thyroglobulin (Tg), thyroperoxidase (TPO) and thyrotropin receptor (TRAB)[1,2]. The most common antibodies frequently measured in serum in population surveys are the thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) [3]. TPOAb has frequently been found in the general population, compared to other antibodies; this antibody directly involved in thyroid cells damage and positively correlated with the activity of chronic autoimmune thyroiditis [5]. In a study by Li et al the 5-yr cumulative incidence of TPOAb-positivity was reported to be 2.81%[4] These differences may be due to genetic, environmental factors (such as iodine intake) and methods applied for antibody measurement [13,14]. Though the prevalence of TPOAb positivity has been investigated in several cross sectional studies, limited longitudinal studies have demonstrated the incidence and natural course of this antibody in the general population. We conducted the present study to analyze the prevalence, incidence rate, and natural courses of TPOAb in a population based study
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