Intelligence quotient in children with congenital hypothyroidism on treatment: A cross-sectional study

Introduction: Congenital hypothyroidism (CH) is the most commonly identified endocrine disorder. Early intervention can prevent intellectual deficits. Objective: To determine the intelligence quotient (IQ) and aetiology in children diagnosed with CH undergoing treatment and the associations between the IQ and the age of diagnosis. Method: A cross-sectional study was conducted in a tertiary care hospital in Bangalore, which enrolled 52 children aged 6 months to 15 years diagnosed with CH. Using a pre-designed proforma, we collected demographic data and confirmed CH aetiology. For IQ assessment, children under 3 years underwent the Vineland Social Maturity Scale (VSMS) and developmental screening test (DST), while those over 3 years were evaluated with the VSMS and Binet Kamat test of intelligence (BKT). Results: Among the 52 children with CH, dyshormonogenesis was the predominant aetiology. In the under-3-year age group (n=17), all demonstrated average to above-average intelligence. Among those over 3 years (n=35), 10.9% (95% CI: 6.5% to 17.2%) exhibited low average and borderline intelligence with the VSMS, and 5.7% (95% CI: 2.3% to 12.5%) had extremely low IQ (IQ <70). The BKT scale showed 20% (95% CI: 12.8% to 29.7%) with low average and borderline intelligence, and 2.9% (95% CI: 0.7% to 8.3%) with extremely low IQ (IQ <70). Children diagnosed at a mean age of 4.2 and 4.4 years exhibited intellectual disability on the VSMS and BKT scales, respectively. Conversely, those diagnosed at a mean age of 1.2 and 1.8 years showed average and above-average intelligence on the VSMS (p-value 0.02) and BKT scale (p-value 0.001), respectively. Conclusions: Children diagnosed with CH at mean ages of 4.2 and 4.4 years exhibited intellectual disability on the VSMS and BKT scales, respectively. Conversely, those diagnosed with CH at mean ages of 1.2 and 1.8 years showed average and above-average intelligence on the VSMS (p = 0.02) and BKT scale (p = 0.001), respectively.