Interleukin-6 and insulin incrase and nitric oxide and adiponectin decrease in blind dogs with pituitary-dependent hyperadrenocorticism

In this study, two populations of dogs with pituitary dependent hypercortisolism (PDH) were compared over a 2-year period. One group had normal vision (Group A, n = 27) and one group was blind (Group B, n = 20). Group B was characterised by the rapid appearance of the clinical signs of PDH that precede blindness. We found increases in pre-adrenocorticotropic hormone cortisol (P = 0.002), IL-6 (P = 0.0001), insulin, and insulin sensitivity (detected with the Homeostatic Model Assessment, P < 0.0001) in Group B but not in Group A. The nitric oxide (NO) and the total adiponectin concentrations decreased (P = 0.0001 and P = 0.02, respectively) in Group B versus Group A. The IL-6 and insulin concentrations and the HOMA-A index were positively correlated with the cortisol concentration and were negatively correlated with the NO concentration. With the exception of adiponectin, the other variables were associated with blindness. We concluded that blindness in PDH is a haemodynamic event associated with metabolic changes, with the increase in the IL-6 concentration and the decrease in the NO concentration affecting the retinal vasculature and producing a high risk of vision loss.