Corticotropin releasing hormone (CRH) and ACTH concentrations in plasma and CRH and IL-6 concentrations in synovial fluid in patients with rheumatoid arthritis (RA) were examined to clarify the relationship between cytokines and the hypothalamic-pituitary-adrenal axis (HPA axis). Concentrations of serum amyloid A protein (SAA), one of the acute phase proteins, were also measured as an indicator of inflammation. CRH and IL-6 concentrations in synovial fluid were higher in RA patients than in control patients (osteoarthritis, OA). Plasma ACTH and CRH levels were significantly lower in RA patients than in OA patients. This suggests that CRH secretion in synovial fluid is regulated differently from plasma CRH secretion, as CRH levels in synovial fluid and plasma showed opposite changes in RA patients. SAA levels were positively correlated with the levels of CRH or IL-6 in synovial fluid, whereas there was no correlation between CRH and IL-6 levels. The results suggest that CRH and IL-6 play important independent roles in producing SAA in synovial fluid.
The Japan Endocrine Society