Background: Although thyroid ultrasound is a valuable tool for the diagnosis and follow-up of patients with Hashimoto's thyroiditis (HT), classical sonographic findings are not always present.
Aim: To calculate the time needed for children with HT and normal ultrasound at diagnosis to develop characteristic sonographic findings.
Patients and methods: 105 children (23 male and 82 female) with HT (mean age 9.4 +/- 2.9 years) were studied. Physical examination and measurements of TSH and fT4 levels were performed at diagnosis, at 3-month intervals for the first year, and twice yearly thereafter. Thyroid ultrasound was performed at diagnosis and twice yearly thereafter. The median follow-up duration was 18 months (range: 6-61 months).
Results: The time needed for 30%, 50%, and 70% of children to demonstrate an abnormal thyroid sonographic pattern was 4, 7, and 14 months, respectively. Important factors accelerating sonographic changes were goiter (p = 0.023), hypothyroidism (p = 0.0255), and seropositivity for both thyroid peroxidase (anti-TPO) and thyroglobulin (anti-Tg) autoantibodies (p = 0.0005).
Conclusion: Sonographic findings of HT are present in 37% of children at diagnosis. Fifty percent of children with normal initial thyroid US will develop changes within 7 months; however, characteristic findings may not develop for over 4 years.