Evaluation of the levels of serum klotho, fibroblast growth factor-23 and vitamin D in children and adolescents aged 6-15 years diagnosed with attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is among the most common psychiatric disorders in children and adolescents, but its etiology remains unclear. As far as can be seen, neurobiological studies investigating the etiology of ADHD have primarily focused on the dopaminergic and noradrenergic systems, neurotrophic factors, and various hormones/neuromodulators. This study aimed to examine levels of klotho, FGF-23, and vitamin D, which are thought to be involved in the etiology of ADHD, and to compare the findings with healthy controls. Our sample consisted of a total of 80 subjects, including 40 cases diagnosed with ADHD who presented with ADHD symptoms to the Outpatient Clinic of Department of Child and Adolescent Psychiatry at Fırat University Faculty of Medicine and met the inclusion criteria of the study, along with 40 healthy control subjects. Sociodemographic data form, Schedule for Affective Disorders and Schizophrenia for School-Age Children Present and Lifetime Version-DSM-5 Version, Conners'Parent/Teacher Rating Scale-Revised Long Form (CPRS-R:L/CTRS-R:L) and DSM-IV-Based Child and Adolescent Behavioral Disorders Screening and Rating Scale were applied to all subjects. All cases were examined in terms of serum klotho, FGF-23 and vitamin D levels. In our study, serum FGF-23 levels were found significantly lower in the case group than in the control group. No significant differences were found between the groups in terms of klotho and vitamin D levels. A significant positive correlation was observed between vitamin D levels and the total scores of the CPRS-R:L DSM-IV hyperactive/impulsive, the CPRS-R:L DSM-IV total and the CTRS-R:L global index—restless/impulsive subscale. There were no significant correlations between klotho or FGF-23 levels and the CPRS-R:L or CTRS-R:L scores. In conclusion, the differences in FGF-23 levels detected in the ADHD group in our study appear to offer a significant area for research. Conducting studies with larger sample sizes and longitudinal designs to reveal the relationship of Klotho, FGF-23, and vitamin D with ADHD could make a significant contribution to understanding the disorder. Key words: Attention deficit hyperactivity disorder, klotho, FGF-23, vitamin D