Seasonal Changes in Plasma Adrenocorticotropic Hormone and α-Melanocyte-Stimulating Hormone in Response to Thyrotropin-Releasing Hormone in Normal, Aged Horses

Abstract

Plasma ACTH and α-MSH responses to TRH administration experience seasonal variation, with TRH-stimulated ACTH and α-MSH concentrations increasing from summer through fall. These results support previous evidence of a seasonal influence on the equine pituitary-adrenal axis. More research is warranted with a larger number of horses to determine if seasonal reference ranges for TRH stimulation testing need to be defined.