Circulating neurohormone imbalances in canine sudden acquired retinal degeneration syndrome and canine pituitary‐dependent hypercortisolism

Background Sudden acquired retinal degeneration syndrome (SARDS) has clinical similarity to pituitary‐dependent hypercortisolism (PDH) in dogs. Some studies have identified a greater frequency of SARDS in seasons with reduced daylight hours. Neurohormone imbalances contribute to retinal lesions in other species, warranting further study in dogs with SARDS. Hypothesis Dysregulation of circulating melatonin concentration is present in dogs with SARDS but not in dogs with PDH. Animals Fifteen client‐owned dogs with spontaneous SARDS (median time of vision loss 18 days), 14 normal dogs, and 13 dogs with confirmed PDH. Procedures Prospective case‐control study. ELISA on samples (obtained in the morning) for measurement of plasma melatonin and dopamine, serum serotonin, urine 6‐sulfatoxymelatonin (MT6s), and creatinine. Statistical analysis was performed using 1‐way ANOVA, Spearman correlation and receiver operator characteristic area under the curve analysis. Results There were no significant differences in circulating melatonin, serotonin or dopamine concentrations between the 3 groups, although the study was underpowered for detection of significant differences in serum serotonin. Urine MT6s:creatinine ratio was significantly higher in dogs with PDH (4.08 ± 2.15 urine [MT6s] ng/mL per mg of urine creatinine) compared with dogs with SARDS (2.37 ± .51, P  < .01), but not compared with normal dogs. Conclusions and Clinical Relevance We have identified neurohormone differences between dogs with SARDS and PDH.