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Most of the recently published papers on Pituitary Pars Intermedia Dysfunction (PPID) hold the view that plasma concentration of adrenocorticotrope hormon (ACTH) does not correlate with the severity of clinical signs in horses. The authors of this study aimed to investigate this hypothesis. Furthermore, it was examined whether a scoring system, based on the severity of clinical signs for PPID, could predict plasma ACTH concentrations and if plasma ACTH is a useful indicator for early detection of the disease. In this study, 100 horses and ponies without prior treatment from the own practice clientele and recruited over flyers and laity press were included. Inclusion criteria implied at least one cardinal clinical sign like delayed shedding of hair coat and/ or hypertrichosis, muscle atrophy, and abnormal fat distribution, recurrent laminitis of unclear etiology, polyuria and polydipsia, changing in behavior, reduced performance, hyperhidrosis, recurrent infections and/ or reduced fertility (in mares). The horses and ponies were examined and classified according to a questionnaire and scoring system. Blood samples were taken for hematology and plasma biochemistry and sent to VetMedLabor IDEXX (Ludwigsburg, Germany). Results of the clinical examination and the score were compared with the plasma ACTH concentrations of the horses. Data was obtained from an equal number of horses (n=46) and ponies (n=54), mostly for leisure use, with a mean age of 20 years (8–40) and an average BCS of 6.5 (2.5–9). Breed, housing and feeding regime had no influence on plasma ACTH. A significant correlation was found with plasma ACTH and regional adiposity/ abnormal fat deposition (P=0.04) as well as with plasma ACTH and hypertrichosis (P=0.0001). The most significant correlation was found for age of the horse or pony and plasma ACTH (P=0.0001). There was a positive, highly significant correlation with PPID-score and plasma ACTH (P=0.0001) but only in horses with ACTH levels above reference range. To sum it up: If plasma ACTH is within the normal seasonal range, the PPID scoring system is not able to detect PPID based on clinical signs. Furthermore, it was not possible to provide ACTH cut-off values and typical clinical signs. Of all parameters, age showed the highest correlation with plasma ACTH levels and seems to be a key indicator for the onset of the disease. Although plasma ACTH levels correlate with the severity of PPID, the scoring system could not predict the actual level of plasma ACTH but helped with the diagnosis of the disease. Either the number of horses and ponies included in this study was not sufficient to identify a link between clinical signs and plasma ACTH or there is none. The late development of obvious clinical signs makes it difficult to diagnose early stages of the disease in young horses, since plasma ACTH does not seem to provide reliable information at young age. The authors recommend further research on this topic to identify reliable indicators for early stages of PPID.