2016 ACVIM Forum Research Abstract Program

Of the 418 enrolled horses, 52.8% were diagnosed with hyperinsulinemia. Based on the combined data of clinical signs (11 interpretable), glucose levels and fasting status, cresty neck, laminitis and high glucose were significant predictors of HI. Specifically, horses with high glucose levels were seen to have almost four times the odds (3.5X) of HI compared to those with normal glucose levels. Therefore, when evaluating horses with suspected endocrine disease, at a minimum, ACTH, insulin and glucose should be evaluated. Long term studies need to be conducted in large populations of horses to further evaluate endocrinopathies in horses. Pituitary Pars Intermedia Dysfunction (PPID) has previously been diagnosed and managed as an older horse disease with advanced clinical signs. However, in early PPID, the clinical signs are typically more subtle. Clinical signs of early PPID include: decreased athletic performance, change in attitude/lethargy, delayed hair coat shedding (subtle), regional hypertrichosis, loss of epaxial muscle mass (topline), regional adiposity, and laminitis. One of the major limitations of diagnostic testing for PPID is the sensitivity of available diagnostic assays. Thyrotropin-releasing hormone (TRH) stimulation test has been shown to have an increased sensitivity of detecting horses with early PPID compared to resting ACTH. Few studies exist concerning endocrinologic testing and follow-up monitoring the clinical progression and diagnostic assay results following treatment in horses with early PPID. The purpose of this study was to identify cases of early PPID based on clinical signs and laboratory testing then determine improvements in ACTH levels using resting ACTH, TRH stimulation test, and clinical signs over time.