Heterogeneity of hypothalamic-pituitary-adrenal system response to a combined dexamethasone-CRH test in multiple sclerosis

The endocrine system participates in the regulation of the immune and neural systems and therefore hormonal factors probably play an important role in the development and course of multiple sclerosis (MS). Specifically, the hypothalamic-pituitary-adrenal (HPA) system seems crucial because (a) the inflammatory response is accompanied by HPA activation; (b) animal models with an inherited HPA defect are prone to developing experimental autoimmune encephalitis: and (c) most important, corticosteroids are still the most widely used treatment. We administered a recently developed neuroendocrine function test that combines dexamethasone suppression (1.5 mg orally at 2300 h) and corticotropin-releasing hormone (CRH) stimulation (100 mu g i.v. at 1500 h the following day) and measured the response of plasma cortisol and corticotrophin (ACTH) secretion in 19 patients with an acute exacerbation of MS. These patients had a significantly higher mean plasma cortisol response than age-matched controls (peak minus baseline; 48.1 +/- 10.5 ng/ml [mean +/- SEM] versus 19.8 +/- 4.2 ng/ml; p < 0.05), but the corresponding ACTH values for the two groups were indistinguishable (13.4 +/- 1.4 pg/ml [mean +/- SEM] versus 11.3 +/- 1.4 pg/ml; n.s.). The response range in the patients was broader and we identified six patients with excessive cortisol release (peak minus baseline: 100.5 +/- 14.4 ng/ml [mean +/- SEM]), whereas four patients failed to respond at all. The hormonal response patterns were not related to previous treatments with corticosteroids or other immunosuppressants or to psychopathological features. These results point to a heterogeneity of HPA system function, most likely at the corticosteroid receptor level, which has clinical implications for all those treatments that affect the HPA system and the course of MS.