Serum (clotted blood)
Cortisol is rarely useful in equine medicine. Equine hyper- and hypo-adrenocorticism are both extremely rare. Common endocrinopathies such as Equine Metabolic Syndrome and PPID have been shown to have similar total cortisol concentrations to those of normal horses. There is some evidence that the free (non-protein bound) fraction of serum cortisol might be increased in PPID or EMS cases, although this requires further investigation and currently access to testing for the free fraction is difficult. Low cortisol levels might be associated with some critical care cases (CIRCI) although replacement therapy is controversial.