Association Between Adrenocorticotropic Hormone Concentration and Clinical Signs of Pituitary Pars Intermedia Dysfunction in Swiss and Austrian Equids

Background

There remains a scarcity of data concerning the relationship between the clinical signs associated with PPID and plasma ACTH concentrations.

Objectives

Report the frequency of clinical signs in the study cohort and identify individual clinical signs or combinations of clinical signs associated with high ACTH concentrations.

Animals

Two hundred eighty equids were examined by private veterinarians.

Methods

A cross-sectional study of animals with clinical suspicion of PPID was conducted between August and November. Private practitioners completed an online questionnaire reporting detailed information, including signalment, owner-reported history, and clinical observations during the examination. Plasma ACTH concentrations of each animal were measured. Associations between clinical signs and ACTH concentrations were examined.

Results

Age, month, and specific clinical signs (hair coat abnormalities, laminitis, and supraorbital fat) were univariably associated with high ACTH concentrations. The first three dimensions of the multiple correspondence analysis (MCA) described the aggregation of clinical signs according to a known semiological typicity. Dimensions 1, 2, and 3 corresponded to features indicative of equine metabolic syndrome, early-stage PPID, and advanced PPID, respectively. Further regression analysis showed that Dimensions 1 and 3, as well as age, were significant predictors of high ACTH levels.

Conclusions and Clinical Importance

The results indicate that particular clinical signs commonly associated with advanced stages of PPID are associated with high ACTH levels. Furthermore, in this data set, a phenotype compatible with metabolic syndrome was also linked to higher ACTH concentrations. These findings underscore the importance of seeking more sensitive biomarkers for the diagnosis of early PPID.