Role of calcium metabolism in ADHD: The relationship between parathyroid hormone and ADHD symptom severity

BACKGROUND: Vitamin D has been found to be associated with the pathogenesis of attention deficit hyperactivity disorder (ADHD). However, the potential role of parathyroid hormone (PTH) is still unclear. AIM: We aimed to investigate the association between calcium metabolism and ADHD symptomatology. METHODS: We included 106 participants aged between 7 and 13 years old (51 ADHD patients, mean age: 9.54 ± 1.77, 55 healthy controls mean age: 9.97 ± 0.94) to this study. K-SADS-PL and Conners’ Parent/Teacher Rating Scales, Stroop Test were performed. Blood samples to measure serum levels of Vitamin D, PTH, calcium (Ca), magnesium (Mg), phosphorus (P), and alkaline phosphatase (ALP) were collected in the spring (March–April–May) to prevent seasonal variability. RESULTS: PTH, P, and ALP values were significantly lower and Vitamin D, Ca, and Mg values were significantly higher in the ADHD group (P < 0.05, for all). Both groups had Vitamin D deficiency. Control group has lower Vitamin D levels than the ADHD group (respectively; 17.66 ± 9.07, 21.99 ± 10.99, P < 0.05). There was a negative correlation between PTH and CTRS hyperactivity, CGI-RI and CGI-EL sub-scores, CGI-Total, DSM-IV-Inattention, DSM-IV Hyperactivity/Impulsivity, DSM-IV-Total scores (P < 0.05, for all). CONCLUSIONS: We found lower PTH levels in ADHD patients and a strong and negative correlation between PTH and symptom severity. Future studies are needed to clarify if these findings are due to the key role of PTH in ADHD pathology or PTH’s function in activating vitamin D.