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

ABSTRACT

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 MT6screatinine 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.