Objectives: Subclinical hypothyroidism (SH) is the most common thyroid abnormality in Down Syndrome (DS) children (25-60%); its etiology remains still not completely clarified. Aim of this prospective multicenter study was to evaluate prevalence and natural course of autoimmune and non-autoimmune SH in a large cohort of DS children and adolescents.
Methods: The study population included 101 DS patients with SH (TSH 5-10 mIU/L; FT4 1222 pmol/L), aged 2-17 years at SH diagnosis. DS children with congenital hypothyroidism or early onset isolated hyperthyrotropinemia were excluded. Annual monitoring of TSH, FT4, BMI and height was performed for 5 years. Thyroglobulin autoantibodies (TGAbs) and thyroid-peroxidase autoantibodies (TPOAbs) were tested at diagnosis and at the end of follow-up.
Results: 37/101 (36.6%) patients displayed autoantibodies positivity (group A); the remaining 64 (63.4%) were classified as non-autoimmune SH (group B), (P=0.0001). Group A was characterized by higher median age at SH diagnosis and by more frequent family history of thyroid disease (6.6 vs 4.7 years, P=0.001; 32.4% vs 7.8%, P=0.001 respectively), whereas congenital heart defects were more common in group B (65.6% vs 43.2%, P=0.028). Gender, median BMI (SDS), height (SDS), FT4 and TSH were similar between the two groups. At the end of follow-up: 35.1% of group A patients developed an overt hypothyroidism (OH) vs 17.2% of group B (P=0.041); 31.25% of group A vs 10.8% of group B became biochemically euthyroid (P=0.02); 37.8% of group A vs 51.5% of group B maintained, over time, SH condition (P=0.183). Overt hyperthyroidism was only observed in group A (16.2%, P=0.004). Logistic regression suggested autoimmunity (OR=3.2) and baseline TSH values (OR=1.13) as predictive factors of evolution from SH to OH.
Conclusions: In DS children, non-autoimmune SH showed higher prevalence and earlier onset. The risk of thyroid function deterioration over time, from SH to OH, seems to be influenced by autoimmune etiology and higher baseline TSH values.
19 - 21 Sep 2019
European Society for Paediatric Endocrinology