Introduction: Subclinical hypothyroidism (SH) is characterized by serum TSH levels above the upper limit of the reference range, in the presence of normal serum concentrations of total T4 and free T4. Associ-ation between SH in childhood and adverse neurocognitive outcomes remains controversial.
Objective: To evaluate the intellectual outcome of children with SH before and after 2 years of treatment with levothyroxine (L-T4).
Methods: Thirty-five children (18 males and 17 females) aged 8.8±0.5 years with persistent, idiopathic and mild SH (TSH serum levels between 4.5 and 10 mUI/L) were enrolled in the study. Thirty-five age- and sex-matched healthy children were enrolled as controls. Twenty-one children underwent a 2 year-course of L-T4 treatment (SH-group 1) whereas 14 refused any treatment (SH-group 2). Intellectual quotient (IQ) was evaluated through the Wechsler Intelligence Scale-revised for children in all subjects at study entry and after two years of therapy in SH-group 1 and two years of clinical observation in SH-group 2.
Results: At baseline, no significant differences were observed between SH children and controls as regards to verbal (VIQ, 98.89±2.43 vs 97.03±2.93) performance (PIQ, 100.91±1.75 vs 106.23±1.82), and full-scale (FSIQ, 99.80±1.98 vs 102.34±2.44) IQs. Moreover IQs at baseline were comparable in both SH-group 1 and SH-group 2 (VIQ 100.76±2.96 vs 96.07±4.03; PIQ 102.19±2.33 vs 99.00±2.63; FIQ 101.52±2.61 vs 97.21±3.00, respectively). Two years of L-T4 treatment in SH-group 1were associated with a normalization in TSH values as compared to baseline (6.21±0.21 vs 3.19±0.40 mUI/L, P<0.0001) but not with an improvement in IQ scores (VIQ 100.33±3.52, PIQ 105.86±3.04, FSIQ 103.67±3.30) as compared to both baseline and untreated SH-group 2 IQ values (VIQ 96.86±3.93, PIQ 99.29±2.60, FSIQ 97.50±2.92).
Conclusions: Our data suggest that persistent, mild SH in children is not associated with intellectual impairment, and that a 2 year-course of L-T4 treatment does not induce any significant improvement in IQ scores.
18 - 21 May 2019
European Society of Endocrinology