Presentation: Functioning of the Hypothalamic Pituitary Adrenal and Growth Hormone Axes are Associated with the Presence of Multiple Chronic Pain Syndromes (2007)

1518 Functioning of the Hypothalamic Pituitary Adrenal and Growth Hormone Axes are Associated with the Presence of Multiple Chronic Pain Syndromes

Purpose: Chronic widespread pain (CWP), irritable bowel syndrome (IBS) and chronic oro-facial pain (OFP) co-occur and share common psychosocial risk factors. The action of these risk factors may be mediated through stress system response including hypothalamic-pituitary-adrenal (HPA) and growth hormone (GH) axis function. The aim of this study was to examine the hypothesis that stress axis function would be associated with the presence of multiple chronic pain syndromes.
Methods: We conducted a population based cohort study. All subjects completed a questionnaire to identify those reporting CWP (ACR criteria), IBS (Rome II) and OFP. Of the 1315 (participation rate 84%) subjects, pain status was available for 1180 (89.7%) of whom 766 (64.9%) reported no symptoms, 277 (23.5%) reported one, and 137 (11.6%) reported 2 or more. We sought to recruit 80 subjects from each group to have a detailed assessment of HPA (morning 8am and evening 10pm saliva, and post-dexamethasone serum cortisol levels) and GH (serum IGF1 levels) axis function. We used ordinal regression to examine the relationship between stress axis function and the presence of symptoms. Subjects reporting no symptoms formed the referent category. All results are expressed as odds ratios (OR) with 95% confidence intervals (CI) adjusted for age and gender. In addition we adjusted for current psychological state using the Illness Behaviour, Health Anxiety, and Somatic Symptoms Checklist scales, and levels of psychological distress using the General Health Questionnaire.
Results: A total of 80 subjects (56% of those invited) with no symptoms, 80 (49%) with one and 72 (69%) with two or more participated in the study. The median age of the groups was similar (52, 51 and 53 years respectively) although women comprised the greater proportion of subjects in the symptom groups (% female: 52, 62, and 69 respectively, p < 0.001). Mean evening saliva cortisol levels increased and IGF1 levels decreased with the number of symptoms reported (cortisol (nMol/L): 0.8, 1.1, 1.9, IGF1 (nMol/L): 15.8, 15.7, 15.4) although these differences were not significant. After adjusting for age and gender, evening saliva cortisol levels were significantly associated, per unit increase in nMol/L of cortisol, with having one (OR = 1.06, 95% CI (1.004, 1.2)) or two and more (1.12, (1.006, 1.3)) symptoms. No other markers of stress response were associated. However, the ratio of cortisol to IGF levels was associated with an increased odds of reporting one (2.8, (0.6, 12.3)) and two or more (6.1 (1.3, 28.2)) symptoms. All of the psychosocial factors independently predicted the onset of symptoms but did not explain the observed relationships.
Conclusion: We have previously shown that HPA function predicts the onset of CWP. The current results suggest that similar alterations may be part of the aetiological pathway for multiple chronic pain syndromes.

 J. McBeth, None; V. Aggarwal, None; D. Ray, None; G.J. Macfarlane, None.

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