Protocol for Testing, Treatment and Management.
Since our last Autumn newsletter, in which we published an article on PPID in horses, there have been some further updates on recommendations for testing, treatment protocols as well as maintenance protocols for horses with PPID.
Diagnosing PPID
Cases of Cushing’s disease are often diagnosed by clinical signs, but confirmation with blood testing is highly recommended. There have historically been three main tests used for diagnosing PPID: the dexamethasone suppression test (DST), Thyrotropin releasing hormone (TRH) stimulation test, and endogenous ACTH test.
While each test has its benefits and limitations, it has become widely accepted that the endogenous ACTH test is the preferred first line method to use when diagnosing PPID.
Even though the endogenous ACTH test is recommended, it is important to note that there is natural variation in monthly values. Previously, most research in this field has been conducted in the Northern hemisphere, where conditions are unlike those experienced here is Southern Australia. A recent study conducted within Australia suggest that normal horses may have a higher endogenous ACTH concentration at certain times of the year compared to those in the Northern hemisphere. Because of this a specific set of laboratory reference ranges have been created for horses in Southern parts of Australia, as well as
for various times during the year.
When is the best time to test my horse for PPID?
Endogenous ACTH is at its highest naturally during the Autumn months. Therefore during this period the test has a higher sensitivity and specificity (meaning the test is more accurate).
Ongoing treatment and management
Once starting on a treatment regime with Pergolide mesylate, monitoring of endogenous ACTH levels is recommended to assess the efficacy of ongoing treatment. The following protocol is now recommended: – Testing 3 months after initiation of treatment – Testing every 12 months This ongoing testing ensures that treatment is effective and also allows for alterations to be made in treatment protocols if required. If you horse is due or overdue for a follow up blood test, give us a call to arrange a visit.
Insulin Dysregulation
Insulin dysregulation is a condition that should also be considered when investigating whether a horse has PPID. It a complex metabolic interact that can occur, most commonly, in overweight ponies and should therefore be considered in horses that are overweight, have cresty necks, or have difficulty losing weight. This can also be tested for at the time of endogenous ACTH testing if required. Watch this space as we will cover Insulin Dysyregulation in further detail in a future issue!