Starting in July, all Adrenocorti-co-tropic Hormone (ACTH) levels rise in horses to prepare their bodies for winter. What is ACTH? It is produced by the pituitary gland. Hormone levels continue to rise into December.
Changes in hormone levels trigger the body to grow the winter coat. ACTH levels are measured in picograms per milliliter (pg/ml). A common upper level for normal horses is 35 pg/ml. Horses with uncontrolled or poorly managed Cushing’s disease, also known as pituitary pars intermedia dysfunction (PPID), can reach 1,000 pg/ml. Levels can be checked with a simple blood test.