Cushing’s Disease in Horses

Cushing’s Disease in Horses


The overproduction of the hormone, cortisol, is a common condition in adult and senior horses called Cushing’s Disease.  Cortisol is produced by the adrenal glands so other names for this disease are hyperadrenocorticism or pituitary pars intermedia dysfunction (PPID).  The increase in cortisol is caused by a benign tumor on the pituitary gland in the brain to trigger the adrenal glands to increase cortisol production.


Hormones have effects on many different organ systems, so the increased cortisol creates a variety of symptoms.  The most obvious symptom of Cushing’s Disease is a change in your horse’s coat.  Their fur becomes coarse, long, wavy and fails to shed out in the spring.  Additional common symptoms are muscle tone loss, pot belly, insatiable appetite and increase thirst / urination.  Many horses experience laminitis as a complication of Cushing’s Disease.  When the horse’s hormones are out of whack, the body becomes more susceptible to infection.  As the disease progresses the horse may have difficulty breathing.  Severe cases can lead to changes in mare’s estrus cycle, lethargy, depression, or neurological problems including a head tilt.


Cushing’s can be difficult to diagnose because there is no specific test for the condition.  If you notice any changes in your horse that were mentioned above it is a good idea to notify your veterinarian.  Evaluation of the horse’s symptoms combined with an increase of sugar & fat levels in a blood test typically point to Cushing’s.  There is no cure for Cushing’s Disease, but many treatments are available to support your horse.  You and your vet will need to closely monitor your horse to ensure that their symptoms are being properly managed, but most Cushing’s horses can still live normal lives.





A case of a pony with cushing’s disease.


Medical implications of obesity in horses – lessons for human obesity.


Seasonal changes in circadian peripheral plasma concentrations of melatonin, serotonin, dopamine and cortisol in aged horses with cushing’s disease under natural photoperiod.


Correlation of pituitary histomorphometry with adrenecorticotrophic hormone response to domperidone administration in the diagnosis to equine pituitary pars intermedia dysfunction.


Immunocytochemical demonstration of proopiomelanocortin-derived peptides in pituitary adenomas of the pars intermedia in horses.