Thyroid morphology and subclinical hypothyroidism in children and adolescents with Williams syndrome.

Objective: To verify the prevalence of morpho-volumetric and functional thyroid abnormalities in young patients with Williams syndrome (WS).
Study Design: Ninety-two patients with WS (49 boys and 43 girls, 0.2-17.2 years of age) underwent evaluation of thyroid function by means of thyroid-stimulating hormone (TSH), fT3, and fT4 measurement. Thyroid ultrasonography was performed in 37 patients. Thyroid antibodies (thyroid peroxidase and thyroglobulin) were measured in all patients with abnormal thyroid function tests.
Results: None of our patients had overt hypothyroidism; 29 patients (31.5%) had subclinical hypothyroidism. Thyroid antibodies were absent in all patients. The prevalence of patients with subclinical hypothyroidism was significantly higher in the younger patients. Ultrasonography revealed morphological or volumetric abnormalities of the thyroid gland in 67.5% of patients; these abnormalities were more frequently observed in the older children.
Conclusions: Subclinical hypothyroidism is a frequent but stable finding in young children with WS. The great majority of patients with WS >10 years, either with normal or hypoplastic thyroid, have normal thyroid function. Therefore, we suggest yearly monitoring of thyroid function and sonographic studies at least once in patients with WS. Treatment should be reserved for the patients with overt hypothyroidism or for those whose thyroid function shows signs of progressive deterioration.