Cognitive impairment correlates with hypothalamo-pituitary-adrenal axis dysregulation in multiple sclerosis

Hypothalamo-pituitary-adrenal (HPA) dysregulation has recently been demonstrated in multiple sclerosis (MS) by means of combined dexamethasone corticotropin-releasing hormone (Dex-CRH) suppression tests. Authors found a correlation with course of disease and to a lesser extent with depressive symptoms. In this study, we aimed to further evaluate whether HPA disturbances in MS are correlated with cognitive impairment, disability status, and fatigue. Dex-CRH tests were performed in a total of 40 patients and 11 healthy controls. Concomitantly, cognitive impairment was evaluated using the symbol digit modalities test and fatigue was assessed by different fatigue severity scales. When comparing patient subpopulations to healthy subjects, Dex-CRH stimulation tests indicated an HPA hyperactivity in primary and secondary progressive MS, while relapsing-remitting patients had response patterns similar to controls. However, results were only significant for one of the six analysed parameters, i.e. area under the curve calculations of ACTH stimulation. Within the patient sample, clear-cut differences emerged between groups of different cognitive impairment, being significant for all ACTH response parameters. Our results suggest an HPA hyperactivation related to increased cognitive impairment. Indicators of HPA axis activation further correlated substantially with neurologic disability, but only moderately with duration of disease and even less with depressive symptoms and fatigue. We conclude that the observed dysregulation is more likely a secondary effect of the extent of brain damage rather than primarily involved in the pathogenesis of MS.