Thank you Dr. Kellon, all very interesting stuff.  FWIW, here's what has happened with my mare since I last posted:

Sat 10/25--on 1mgPrascend x7d--feels fantastic!--blood drawn for ACTH/Insulin/Lyme--appe good
Sun 10/26--6mile hunter pace--mare feels incredibly good! best in years, her old self--appe good
Mon 10/27--Flu/rhino Vx IM--appe still good
Tues 10/28--depression, sore neck--500# Banamine PO--appe moderate
Wed 10/29--feels terrible under saddle, like when insulin spikes--now PU/PD--appe good
Thu 10/30--I increased pergolide to 1.5mg/day--appe good--did not ride--still PU/PD
Fri 10/31--expected depression, diarrhea, "spaciness", decreased interest in food from incr. pergolide

It may be pure coincidence, but I feel the vaccine worsened her IR and/or PPID.  She felt horrible under tack on Wed, just as she does when her hyperinsulinemia becomes clinical (historically, in the 60s).  I decided to increase her perg dose by 0.5mg to somehow "control" her too-high insulin until I could figure out what caused it to spike (a seasonal blip?  stress from the hunter pace and/or vaccine?  not high enough perg dose?)  Probably not a wise decision to just increase meds on my own, but my mare has lived on the edge of refractory hyperinsulinemia for so long now that I feel i have nothing else to lose.  Diet no longer works, nor a stringent exercise program.  So the main question on my mind right now is:  is my target dose of pergolide the one that controls her hyperinsulinemia?  She showed great response to seven days of 1mg/day. In fact here are her before and after bloodwork results:

Sep 24, 2014 -- PRE-pergolide (@ Cornell) on strict diet/exercise program:
ACTH...36.6pg/mL (9-36)
Glucose...113mg/dL (71-113)
Insulin...64.99uU/mL (10-40)
Leptin...4.19ng/mL (1-4)

Oct 14, 2014 -- started 0.5mg Prascend, tritrating up by 0.25mg every few days
Oct 19, 2014 -- at 1mg Prascend/day

Oct 25, 2014 -- recheck bloodwork, 7 days at 1mg Prascend (@ Cornell):
ACTH...26.2pg/mL (see above)
Glucose...108mg/dL**
Insulin...45.11uU/mL
Leptin...pending

**Cornell ran glucose off the serum tube I submitted for lyme instead of the plasma sample I sent for the ACTH.  Glucose might be falsely low by a few points because i didnt' spin the serum tubes immed after drawing.  (I assumed lab would run glucose off of the same sample that that use for insulin...)

To summarize, mare felt great and appeared clinically "good" on the 1mg pergolide (x7d) with an insulin testing in the 40s (interestingly, Cornell considers normal insulin to be 10-40uU/mL, while Antech only considers normal to be less than/equal to 20uU/mL).  In the past, way before pergolide, I could get her insulin down into the 20s by diet alone, and mare felt good (stumbling/stiffness resolved) but she had no energy.  Now, with addition of pergolide, mare's body felt great AND she had plenty of energy to spare---until Black Monday, the Day of the Vaccine(10/27). 

I've read much about what to expect to experience BEFORE pergolide, but not much exists in that annals about what to expect AFTER starting pergolide (what is my target dose?  should I expect & pursue complete control of IR? good control of IR?  when does the seasonal endogenous cortisol spike typically decrease?  How do I know if I should try decreasing pergolide during the "down" season?)  I welcome all advisement and opinions.

Thanks so much,
Kerry in NY
Sept 2014

PS I will update my mare's history ASAP.  I need to add the above bloodwork, that's really all that's missing.