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- Pituitary pars intermedia dysfunction (PPID)
- Adrenocorticotropic hormone (ACTH)
- Stress response
Increased adrenocorticotropic hormone (ACTH) concentrations in venous blood are an important indicator of pituitary pars intermedia dysfunction (PPID) in horses (van der Kolk and others 1995). However, a physiological response to stress also elicits an increase in ACTH concentration (Alexander and others 1988). It is currently unknown in horses if symptoms of a stress response are associated with venipuncture and could lead to increased ACTH concentrations and subsequent misinterpretations in the diagnostic work-up of PPID. The objective of the present study was therefore to evaluate whether venipuncture would lead to an immediate increase in the plasma ACTH concentration. We hypothesised that (1) plasma ACTH concentrations increase within one to two minutes after venipuncture, potentially leading to misclassification regarding PPID affection; and that (2) this increase is associated with an increased behavioural stress response.
Fifteen horses aged between 7 and 27 years with a mean age of 18.9±1.3 (se) and comprising of nine mares, five geldings and one stallion were included in the study. All horses showed at least one clinical sign associated with PPID (hypertrichosis, delayed shedding of the winter coat, laminitis, loss of muscle mass, abnormal fat distribution or signs of chronic infections like sinusitis or dermatitis) (van der Kolk and others 1993; McGowan and others 2013). Paired samples were analysed in two horses during the autumn season (August–October) and the remaining 13 individuals during the rest of the year (November–July). In all horses, the left …