**10. Laboratory findings**

Although the level of TSH may be slightly or even moderately raised in some individual's thyroid function tests are often normal, termed subclinical hypothyroidisms (37). In a study from iodine-replete area, twenty-four patients (21%) were euthyroid, 48 (42%) had compensated hypothyroidism, and 42 (37%) had hypothyroidism (including two patients with transient hyperthyroidism reversed to hypothyroidism within weeks). There was no difference in clinical symptoms of hypothyroidism by thyroid status, except for a higher rate of constipation in the hypothyroid group (38). The fact that many children with lymphocytic thyroiditis do not have elevated levels of TSH indicates that the goiter may be caused by the lymphocytic infiltrations or by thyroid growth-stimulating immunoglobulins.

In normal individuals, positive anti-TPO were detected in 13.0 ± 0.4%, and positive Anti-Tg was detected in 11.5 ± 0.5%. The prevalence of positive antibodies was lower in the diseasefree population: Anti-TPO, 11.3 ± 0.4% and Anti-Tg, 10.4 ± 0.5%. The prevalence of positive Anti-TPO and positive Anti-Tg in the total and disease-free population was higher in females than males (P< 0.001) and increased with age, especially among females. Approximately 18% of the disease-free population had detectable Anti-Tg or Anti-TPO of those with positive Anti-Tg, 69.9% also had positive Anti-TPO; and of those with positive Anti-TPO, 54.5% also had positive Anti-Tg. Anti-TPO was positive alone in 4.4%, and Anti-Tg was positive alone in 3.4%. Anti-TPO and Anti-Tg were detected together in 6.9% (59).

Almost all young children with HT have serum antibody titres to TPO, but the anti-Tg test for thyroid antibodies is positive in fewer than 50%. Antibodies to TPO and Tg are found equally in adolescents with HT. When both tests are used, approximately 95% of patients with thyroid autoimmunity are detected. Levels in children and adolescents are lower than those in adults with HT, and repeated measurements are indicated in questionable instances because titres may increase later in the course of the disease (37). Results about decreasing Anti-TPO under LT4 treatment have been found variable with 10% and 90% after a followup of 6 to 24 months (60,61). Decreasing Anti-TPO under LT4 treatment appears to depend on time, a 45 % decrease after 1 year and a 70% decrease after 5 years (62).
