The Sardinian autoimmunity study: 3. Studies on circulating antithyroid antibodies in Sardinian schoolchildren: Relationship to goiter prevalence andthyroid function

The relationship among iodine intake, goiter prevalence, and thyroid autoim munity remains controversial. In the present article, we report the prevale nce of antithyroid antibodies (ATA) in relation to iodine intake, frequency of goiter, and thyroid function in a large group of Sardinian schoolchildr en living in areas with borderline iodine sufficiency, or mild to moderate iodine deficiency. A total of 8,040 schoolchildren (4,194 males, 3,846 fema les, ages 6-15 years) from 29 communities were examined between 1986-1994. Thyroid size was assessed by palpation, according to the Pan American Healt h Organization (PAHO) criteria. In all cases anti-microsomal (MAb) or antit hyroid peroxidase antibodies (TPOAb) and thyrotropin (TSH) were assayed. Ur inary iodine was determined in a subgroup of 820 children. ATA was detected in 235 (2.92%) sera (88 males, 2.12%; 147 females, 3.82%; X (2) = 20.41, p < 0.0001). ATA prevalence ranged between 0.0%-7.3% in the 29 communities w ithout any geographical correlation with goiter prevalence and urinary iodi ne excretion. However, ATA was more frequently detected in goitrous childre n, especially in females. The presence of ATA was not age-dependent in male s, whereas a significant increase of ATA was observed in females older than 11 years of age. Seventy-seven (0.96%) children showed borderline to sligh tly increased serum TSH (>5.2-32 mU/L). Increased serum TSH concentration w as more frequently found in children with ATA, especially at higher titers. In summary, our study in Sardinian schoolchildren indicates: (1) ATA displ ay geographical heterogeneity, which seems to be unrelated to goiter preval ence and/or to iodine supply; (2) ATA axe more frequently detected in femal es older than 11 years of age, suggesting that puberty has a role in determ ining the predominance in females of thyroid autoimmunity; (3) although mos t goitrous children are ATA-negative, the prevalence of ATA is increased in children with enlarged glands; (4) ATA is associated with an increased pre valence of subclinical hypothyroidism.