Clinical implications of using adrenocorticotropic hormone diagnostic cutoffs or reference intervals to diagnose pituitary pars intermedia dysfunction in mature horses.

Background: Diagnosis of pituitary pars intermedia dysfunction (PPID) is problematic because of large variations in ACTH concentrations.

Hypothesis/objectives: Compare the test characteristics of baseline and post-thyrotropin-releasing hormone (TRH) stimulation plasma ACTH concentrations in horses using diagnostic cutoff values (DCOVs) and reference intervals (RIs) and determine the clinical consequences of using each method.

Animals: One hundred six mature horses: 72 control cases and 34 PPID cases.

Immunoreactive insulin stability in horses at risk of insulin dysregulation.

Background: Diseases associated with insulin dysregulation (ID), such as equine metabolic syndrome and pituitary pars intermedia dysfunction, are of interest to practitioners because of their association with laminitis. Accurate insulin concentration assessment is critical in diagnosing and managing these diseases.

Hypothesis/objectives: To determine the effect of time, temperature, and collection tube type on insulin concentrations in horses at risk of ID.

Evaluation of combined testing to simultaneously diagnose pituitary pars intermedia dysfunction and insulin dysregulation in horses.

Background: The thyrotropin-releasing hormone (TRH) stimulation test and the 2-step insulin sensitivity test are commonly used methods to diagnose, respectively, pituitary pars intermedia dysfunction (PPID) and insulin dysregulation (ID).

Objectives: To investigate the diagnostic value of combining the TRH stimulation test and the 2-step insulin sensitivity test to diagnose PPID and ID simultaneously.

Animals: Twenty-seven adult horses, 10 control horses without PPID or ID, 5 horses with PPID only, 5 horses with ID only, and 7 horses with PPID and ID.