Screening for hypothyroidism in schools for children with learning difficulties in Southeastern Nigeria

Congenital hypothyroidism (CHT) is a leading cause of preventable mental impairment worldwide, and newborn screening programmes have been adopted by many countries as a means of early detection and treatment of infants with CHT [1]. In Nigeria, there are no screening programmes for CHT and no prevalence studies on hypothyroidism and its contribution to neurodevelopmental problems. Our aim was to establish whether thyroid dysfunction was a common problem in children attending schools that included healthy and learning impaired children. Children <18 years old attending two schools for the learning disabled located in Enugu and Abakaliki (SE Nigeria) underwent measurement of thyroid-stimulating hormone (TSH) and thyroxine (T4). Enugu and Abakaliki are two of the major towns in the southeastern part of Nigeria, with an estimated population of 900,000. Schooling is integrated and so healthy and learning disabled children learn together. Intelligence was assessed using the Draw-A-Person Test as validated for Nigerian children [2]. A Draw-A-Person Quotient (DAPQ) score of <75% is considered learning disabled. Biochemical analysis was by a time-resolved fluoroimmunoassay (AutoDELFIA) neonatal TSH and neonatal T4 kit. The intra-assay variation for TSH and T4 was 6.1% and 14.9%, respectively, whereas the inter-assay variation was 9.0% and 10.0%, respectively. The cutoff value for a normal TSH was taken as <10 mU/l, whereas the cutoff for a normal T4 was taken as >1.6 mg/dl [3]. The study was approved by the ethics committee of the Ebonyi State University Teaching Hospital Abakaliki and written informed parental consent obtained. A total of 117 pupils (63 male) aged 3–18 years from the two schools were studied, and none was already on T4 therapy. Thirty-three children were considered to be healthy, with the remaining children having autism (8), cerebral palsy (13), Down syndrome (16), learning disability (15) and mental retardation (32). The patient characteristics and biochemistry are detailed in Table 1. The mean height of healthy children was greater than the other children (p ¼ 0.02). No patient had either an elevated TSH or a low T4, although the mean TSH level was higher in healthy children without an underlying diagnosis (p ¼ 0.002). Children with a higher IQ (DAPQ > 75%) had a significantly higher TSH (1.22 mU/l) compared with those with an IQ < 75% (0.82 mU/l) (p ¼ 0 < 0.01), and the mean T4 of those with an IQ > 75% (3.67 mg/dl) was higher than that of those with an IQ …