CONCLUSIONS: ADHD may exhibit a consistent pattern of HPA-axis hypoactivity, affecting both basal secretion and stress responsiveness, whereas ACTH, CAR and HCC appear preserved. The effect is strongest in the ADHD-HI subtype and when cortisol is measured in blood, indicating a subtype-specific and matrix-dependent neuroendocrine phenotype. These findings may support HPA-axis dysregulation as a potential biological correlate of ADHD.
