Help understanding TRH stim test results


I'm wondering if someone could help me understand my pony's TRH stim test results...

First tested 5/2020:  ACTH pre: 23.3, post: 335.  Started on 1mg pergolide (pracend).  

Recently tested again 3/2021: ACTH pre: 25.3, post 288.  Vet says everything looks good and maintain on 1mg pergolide.  

So, my question...  Should he have a lower post TRH level if he was on the right amount of pergolide?  To me, those numbers look more or less the same, so either I'm not understanding how pergolide works, or how to interpret the results.

I updated my case history, too, in case you need more details.

2021, Ohio

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