There has been enough research to make “seasonal rise” testing using the ACTH method pretty accurate. My vet will be here this morning to re-test my IR/Cushings horse who gets a blood draw every six months with consistent readings. However, I sort of expect his numbers to be higher this time, not due to seasonal rise but due to what I see
Far as the TRH test —- it’s personal choice for everyone but this involves injecting 25ml of something into the horse and I’m not doing that -nupe - no - not in this lifetime.
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“
Thyrotropin releasing hormone stimulation test (TRHST)
This is currently considered the most accurate test for the diagnosis of PPID. The test relies on an excessive pituitary response to the administration of Thyrotropin-releasing hormone (TRH) in horses with PPID when compared to normal horses.
However, the test still has limitations and ongoing research is needed to help us fully understand how to interpret the results. This test is appropriate when the results of a basal ACTH test have been equivocal, or in a case in which PPID is still suspected despite a negative ACTH test result.
Sampling protocol
- Collect an EDTA sample for baseline measurement of ACTH
- Inject 1mg TRH intravenously
- Collect a second EDTA sample exactly 10 minutes later
- The plasma should be handled as described in the ACTH section
Availability of TRH
Pharmaceutical grade TRH is not available on the veterinary or human markets in the UK.
Chemical grade TRH can be cheaply purchased from here
https://phoenixpeptide.com - the specific product is listed
here. We believe this to be legal via the cascade but full VMD guidance can be found
here.”
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SOURCE OF QUOTE:
https://www.rossdales.com/laboratories/guides/ppid-diagnosis