Subclinical Hypothyroidism as the Most Common Thyroid Dysfunction Status in Children With Down's Syndrome.

Subclinical hypothyroidism (SH) was the most common thyroid dysfunction in children with Down's syndrome, affecting 87% of the study cohort.

• 73 DS patients were analyzed (32 girls and 41 boys, mean age at baseline 3.0 ± 4.5 years)
• 63/73 (87%) children were diagnosed with SH
• The study was retrospective, covering patients referred to the Endocrinology Outpatient Clinic between 2010 and 2015, observed until end of June 2019
• Children with congenital hypothyroidism, acute lymphoblastic leukemia, seizures, or treatment with interfering drugs were excluded

The majority of SH children with Down's syndrome were treated with levothyroxine (L-T4), while a minority were followed without treatment.

• 47/63 (74.6%) SH children received L-T4 therapy (group SH-T1) with a mean dosage of 1.8 ± 1.0 µg/kg/day
• 16/63 (25.4%) patients were followed up without treatment (group SH-T0)
• Treatment decision reflected clinical practice during the study period

Levothyroxine supplementation did not improve growth in children with Down's syndrome and subclinical hypothyroidism.

• ΔhSDS was 0.1 ± 1.3 (range -2.1 to 3.8) in SH-T0 vs. 0.0 ± 0.7 (range -1.7 to 1.4) in SH-T1, p = 0.96
• No statistically significant difference in height SDS change between treated and untreated groups

Levothyroxine supplementation did not improve BMI in children with Down's syndrome and subclinical hypothyroidism.

• ΔBMI Z-score was 0.3 ± 0.9 (range -0.9 to 2.6) in SH-T0 vs. 0.3 ± 1.1 (range -2.1 to 2.9) in SH-T1, p = 0.65
• No statistically significant difference in BMI Z-score change between treated and untreated groups

Positive antithyroid autoantibodies were detected in a minority of Down's syndrome children with subclinical hypothyroidism.

• Positive anti-TPO and anti-TG antibodies were detected in 7/63 (11.1%) DS cases with SH
• Overt hypothyroidism developed particularly in females with mostly positive titer of antithyroid autoantibodies
• A small percentage of patients progressed to overt hypothyroidism overall

Thyroid dysfunctions have been reported in up to 54% of children with Down's syndrome according to prior literature.

• This figure is cited in the abstract as background context for the study
• The study aimed to investigate the course of SH in DS children and evaluate risk of developing overt thyroid disease and autoimmunity