As I've said before, the only correct dose of pergolide is the one that controls the ACTH - whether it's 1 mg or 10 mg, or more.  In the rare instance where pergolide is not working you can go to cabergoline (injection every 7 to 10 days) but again the dose is what corrects ACTH.

Your vet may be thinking that because APF is an adaptogen it will control ACTH. All adaptogens can modulate the normal ACTH - cortisol axis, some by lowering ACTH, some by substituting for ACTH but PPID is NOT a normal situation and doesn't respond in the same way as the normal axis. Adaptogens don't take months to work. They begin to have measurable effects virtually immediately.

The most difficult PPID horses to control are those that have advanced disease before treatment is started. Monte was showing weight and shedding issues as long ago as 2016, started pergolide in 2019 but with some long periods of also getting Chastetree berry which could block pergolide effects. My opinion would be to get after him aggressively with the pergolide dose - and have the blood sent to Cornell and processed as they describe. I don't trust your results.
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Eleanor in PA

www.drkellon.com 
EC Owner 2001