Underlying Hashimoto's thyroiditis negatively affects the evolution of subclinical hypothyroidism in children irrespective of other concomitant risk factors

Background: The pediatric literature does not contain any studies comparing the evolution of Hashimoto's thyroiditis (HT)-related subclinical hypothyroidism (SH) with idiopathic SH longitudinally. Aim and design: In the present study, the two-year evolution of HT-related SH in 32 children with no concomitant risk factors (group A) was compared to that observed in 90 age-matched children with idiopathic SH (group B). The aim was to ascertain whether the association with HT could, per se, affect the evolution of thyroid status over time in SH children irrespective of other coexisting factors, such as thyromegaly, association with other autoimmune diseases, and/or concomitant therapies. Results: During the two-year follow-up, the percentage of children whose thyrotropin (TSH) values increased >10mIU/L was significantly higher in group A (p<0.0005), whereas the percentages of those who either maintained a stable TSH (5-10mIU/L) or normalized the TSH (<5mIU/L) were significantly higher in group B (p<0.025). Moreover, the percentage of children who developed a pathological thyroid enlargement during follow-up was significantly higher in group A (p<0.0005). Conclusions: The association with HT exerts a negative influence on the evolution over time of mild SH, irrespective of other concomitant risk factors. In children with mild and HT-related SH, the risk of a deterioration in thyroid status over time is high (53.1%), while the probability of spontaneous TSH normalization is relatively low (21.9%). In contrast, in children with mild and idiopathic SH, the risk of a deterioration in thyroid status over time is very low (11.1%), whereas the probability of spontaneous TSH normalization is high (41.1%).