Cushing's Disease Behavior in Horses

Cushing's Disease refers to the pituitary gland overproducing the hormone ACTH which in turn stimulates the adrenal gland to overproduce the essential steroid cortisol. Cushing's Disease is also called "Pituitary Pars Intermedia Dysfunction" and "hyperadrenocorticism." It is thought that a benign tumor on the pituitary gland is the underlying cause of these changes.

  1. First Signs

    • Watch for retention of winter coat.

      A middle-aged horse that does not shed its winter coat is exhibiting a classic sign of Cushing's Disease. Although retention of the winter coat is often the first indicator of a problem, the horse exhibiting this sign has probably has had Cushing's Disease for a while.

    Lethargy

    • Performance horses require special nutrition.

      Many horses who have been diagnosed with Cushing's Disease exhibit lethargy--an overall lack of energy. In order to rule out other causes, your horse's veterinarian will ask questions to, for example, ensure that the horse is receiving adequate nutrition for the level of work the horse is required to perform.

    Other Symptoms

    • A horse with Cushing's Disease may exhibit a "hay belly" without being overfed. The hay belly will also result in a slightly swayed back.

    Blood Tests

    • Your veterinarian will want to conduct blood tests to look for more definitive indicators of Cushing's. Blood tests in horses suspected of Cushing's Disease may show an increased level of ACTH, low levels of T3 and T4 hormones indicating underactive thyroid and slight anemia.

    Other Complications

    • Cushing's can cause a depression of the immune system making a horse susceptible to secondary infections such as skin infections and hoof abcesses. Cushing's is also often accompanied by a tendency toward insulin resistance. Horses with insulin resistance may drink excessively and therefore urinate frequently.

    General Conclusion

    • There are no definitive behaviors associated with Cushing's Disease. Instead, a collection of behaviors and symptoms demonstrates the need to do blood testing to further isolate the cause of the symptoms.