Thyroid autoimmunity in schoolchildren in an area with long-standing iodine sufficiency: correlation with gender, pubertal stage, and maternal thyroid autoimmunity.

Background: A strong genetic background and gender are believed to be involved in thyroid autoimmunity (TA). The age these factors become manifest is less clear, however. The objective of the present study was to determine the prevalence of TA in children and adolescents and to determine if there are relationships between the period of onset of TA and gender and between TA and maternal autoimmunity.

Methods: Antithyroperoxidase antibodies (anti-TPO Ab), antithyroglobulin antibodies (anti-Tg Ab), thyrotropin, thyroxine, triiodothyronine, and urinary iodine were determined in 440 healthy schoolchildren (200 boys and 240 girls), aged 5-18 years, and in 123 mothers living in an iodine-replete region.

Results: The prevalence of positive anti-TPO and anti-Tg Ab was 4.6% and 4.3%, respectively. In girls, the prevalence of positive anti-TPO Ab was higher in Tanner stage II-V compared to Tanner stage I (8.2% vs. 2.2%; p < 0.05). No difference was detected with regard to anti-Tg Ab. In girls, positive anti-TPO and anti-Tg Ab levels were associated with significantly greater thyroid volume. Hypoechogenicity was detected in 52.6% and 36.8% of the children with positive anti-TPO or anti-Tg Ab, respectively (p = 0.0005). The prevalence of autoimmune thyroiditis, as defined by positive serum anti-TPO and/or anti-Tg and an echographic pattern of the thyroid gland having diffuse or irregular hypoechogenicity, was 2.5%. Mothers of anti-TPO Ab positive children had positive anti-TPO Ab more frequently compared to mothers of anti-TPO Ab negative children (82% vs. 18%; p = 0.0005). Mothers of anti-Tg Ab positive children had positive anti-Tg Ab more frequently compared to mothers of anti-Tg Ab negative children (75% vs. 25%; p = 0.0005).

Conclusions: These findings demonstrate that thyroid antibody positivity in children was significantly associated with maternal autoimmunity and their development in girls emerges at puberty. Since heredity, female gender, and puberty are strongly associated with TA, girls in families with TA should be examined at the onset of puberty.