Thyroid dysfunction in attention-deficit hyperactivity disorder and effect of comorbidity

Abstract

Introduction Attention-deficit hyperactivity disorder (ADHD) is considered to have a biologic basis, but the precise cause is unknown. It is one of the neurodevelopmental abnormalities observed frequently in children with generalized resistance to thyroid hormone, suggesting that thyroid abnormalities may be related to ADHD. Aim To assess thyroid dysfunction in children with ADHD and to detect the most common comorbidity. Participants and methods This was a case-control cross sectional study, in which 30 ADHD children were recruited from the Kasr Aini Pediatric Hospital (Abu-El Rish) outpatient psychiatry clinic and compared with 14 healthy control children, siblings of the patient group who participated in this research. Psychometric procedure The Stanford Binet Intelligence Scale, the Arabic version of Conners' Parent Rating Scale-Revised-Long version, and social score were used to calculate social standards of families. Laboratories assessment Serum total T3, total T4, and thyroid-stimulating hormone were assessed using the enzyme-linked immunosorbent assay. Results About 80% of the participants were males and 20% were females. Diagnosis according to the Diagnostic and statistical manual of mental disorders, 4th ed. (DSM-IV) showed that 29 (96.7%) of the patients were diagnosed with ADHD combined type by DSM-IV and only one patient (3.3%) had ADHD inattentive type. Forty percent of the patients were from low socioeconomic class, followed by 26.7% from moderate socioeconomic, and a very low socioeconomic class; however, 6.6% were from a high socioeconomic class. There was a statistically significant difference between cases and control groups in all components of Conners' Parent Rating Scale; all cases had higher means than the control group (P = 0.001). There was no significant difference between both the study group and their siblings in serum total T3, thyroid-stimulating hormone, T4 (P > 0.05). Fifty percent of the patients had no or only one comorbidity and 15 (50%) had two or more comorbidities. On comparing the two subgroups (group with no or one comorbidity and the other group with two or more comorbidities), we found that there were no statistically significant differences between the two groups in the IQ components test. There were only statistically significant differences between two subgroups in the social problem subscale of Conners' scale, which showed higher scores in the subgroup of patients with two or more comorbidities. Also, there were no statistically significant differences in the thyroid profile of the two subgroups and the thyroid functions were within normal. Conclusion Oppositional defiant disorder was the most common comorbidity. Social problems are common in children with ADHD with comorbidity. Children with ADHD have no thyroid dysfunction.