Anti-TNF antibody therapy does not change serum levels of cortisol binding globulin in patients with rheumatoid arthritis but it increased androstenedione relative to cortisol

Objective: Cortisol binding globulin (CBG) is produced by liver cells and is inhibited by proinflammatory cytokines such as IL-6. CBG serum levels are typical low during prolonged inflammatory processes. Thus, observed changes of cortisol during anti-TNF therapy may be related to changes of CBG in RA. This study aimed at investigating the course of CBG during anti-TNF therapy in RA. Methods: In this longitudinal study with subcutaneous adalimumab, 13 long-standing RA patients without prior prednisolone were included. Results: Upon treatment with anti-TNF, we observed a strong decrease of clinical markers of inflammation and serum IL-6. Serum levels of cortisol, CBG, and the ratio of cortisol/CBG did not markedly change, whereas the ratio of serum CBG / IL-6 increased (p=0.004). In parallel, levels of ACTH decreased during the observation period. The ratio of the adrenal androgen androstenedione divided by serum cortisol increased during the observation period (p=0.036). Conclusions: This study demonstrates relatively normal levels of CBG and a normal ratio of CBG / cortisol during anti-TNF therapy. Thus, earlier observed changes of cortisol in relation to IL-6 during anti-TNF therapy may not be related to changes of CBG. This study further confirmed some of our earlier data with infliximab in another cohort.