| Summary: | 碩士 === 國立中興大學 === 獸醫學系暨研究所 === 104 === Cushing’s syndrome is recognized as one of the most common endocrinopathies occurring in dogs, which will cause clinical symptoms and signs due to prolonged exposure to excess corticosteroid. Cortisol is the principle glucocorticoids released by adrenal cortex and is mainly regulated by the hypothalamic-pituitary-adrenocortical axis (HPA). Besides, cortisol is released into blood as pulsation, the number of secretory pluses in dogs was reported to be around 10 in 24 hours. As plasma cortisol concentration is easily to be affected by stress, and about 1-2% cortisol is excreted in the urine unaltered. Therefore, measurement of urinary cortisol/creatinine ratio (UCCR) provides an integrated assessment of cortisol over a period of time and adjusts for fluctuations in plasma levels caused by the pulsatile release of cortisol. The aim of the study was to investigate the urinary cortisol levels in healthy neutered and intact dogs and its daily fluctuations and whether the gonadal hormones would affect the cortisol concentration in urine. Twelve healthy dogs (n=12) from private owners were distributed into 2 groups (n=6/group): Neutered group (n=6) and Intact male group (n=6). Midstream voided urine samples were taken by each owner at home for three consecutive days at 8:00, 12:00 and 16:00 every day when dogs were taken outside and walked. Cortisol and creatinine concentrations were measured and calculated for the cortisol/creatinine ratios. Results indicated that urinary cortisol/creatinine ratios (UCCRs) had considerable variations both within and among dogs, but there was no consistent time of day fluctuation and with no significant variations at 8:00, 12:00 and 16:00. In addition, UCCRs were significantly higher in intact male dogs than in the neutered ones at 12:00 and 16:00, but it was not distinct at 8:00. In conclusion, there was no consistent time of day fluctuation and significant variations at different times of UCCR in dogs. Cortisol concentration is higher in the intact male dogs than the neutered dogs. Urine sample for UCCR detection should be taken in the morning.
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