Multiple adrenocortical steroid response to administration of exogenous adrenocorticotropic hormone to hospitalized foals.

Background The hypothalamic-pituitary-adrenal axis regulates the response to sepsis-associated stress. Relative adrenal insufficiency or adrenocorticotropic hormone (ACTH):cortisol imbalance, defined as a poor cortisol response to administration of ACTH, is common and associated with death in hospitalized foals. However, information on other adrenal steroid response to ACTH stimulation in sick foals is minimal. Objective To investigate the response of multiple adrenocortical steroids to administration of ACTH in foals. Animals Hospitalized (n = 34) and healthy (n = 13) foals. Methods In this prospective study, hospitalized foals were categorized into 2 groups using cluster analysis based on adrenal steroids response to ACTH stimulation: Cluster 1 (n = 11) and Cluster 2 (n = 23). After baseline blood sample collection, foals received 10 mu g of ACTH with additional samples collected at 30 and 90 minutes after ACTH. Steroid and ACTH concentrations were determined by immunoassays. The area under the curve (AUC) and Delta(0-30) were calculated for each hormone. Results The AUC for cortisol, aldosterone, androstenedione, pregnenolone, 17 alpha-OH-progesterone, and progesterone were higher in critically ill (Cluster 1) compared to healthy foals (P < .01). Delta(0-30) for cortisol and 17 alpha-OH-progesterone was lower in Cluster 1 (24%, 26.7%) and Cluster 2 (16%, 11.2%) compared to healthy foals (125%, 71%), respectively (P < .05). Foals that died had increased AUC for endogenous ACTH (269 versus 76.4 pg/mL/h, P < .05) accompanied by a low AUC for cortisol (5.5 versus 15.5 mu g/dL/h, P < .05), suggesting adrenocortical dysfunction. Conclusion and Clinical Importance The 17 alpha-OH-progesterone response to administration of ACTH was a good predictor of disease severity and death in hospitalized foals.