The insulin tolerance test and ovine corticotrophin-releasing-hormone test in episodic cluster headache II: Comparison with low back pain patients

Hypothalamic involvement has been invoked to explain the periodicity of the cluster periods and rhythmicity of the pain attacks in cluster headache. To explore this hypothesis the ovine corticotrophin-releasing hormone (o-CRH) and the insulin tolerance test were administered to a group of episodic cluster headache sufferers during both cluster period and remission. A group of low back pain patients and healthy subjects comprised the control populations. For the o-CRH test, 7 healthy subjects, 7 low back pain patients, 6 cluster headache patients in remission, and 12 in cluster period were studied. Five healthy subjects, 7 low back pain patients, 6 cluster headache patients in remission, and 9 in cluster period were administered the insulin tolerance test. Significantly increased basal cortisol levels were found in cluster headache patients in both illness phases (p <0.0001), but not in low back pain patients. Significantly reduced cortisol response to the o-CRH test was observed in cluster headache patients in both phases compared to healthy controls (p <0.02). A blunted ACTH and cortisol response (p <0.0001 and p <0.003 respectively) to the insulin tolerance test was present in cluster headache patients in both phases of the illness compared to healthy subjects and low back pain patients. On the contrary, the ACTH surge after insulin induced hypoglycemia was significantly increased in the low back pain patient group (p = 0.02). These results suggest that the altered hypothalamic-pituitary-adrenal axis responsiveness in cluster headache patients is not a consequence of the pain, and point to a central, probably hypothalamic derangement in this pathology.