ACTH shot up to 45. Should I re-test in February?

Karin Sherbin

I have 2 questions, but first brief context:

I have free-leased Inky to a lesson barn for 2 years and the trainer has been responsible for his care and testing. He outwardly seems to be in better shape than when he was being boarded and I rode him little or not at all (he used to crow-hop and buck under saddle. Now he doesn't).

I updated the case history as best I could (e.g., type of feed, but not amounts. It took 3 months to get his ACTH test result so it's been difficult to keep up the details).

The bottom line: Inky was off his pergolide "for a few days" due to shipping delays from the compounding pharmacy (the one in AZ) when he had his blood draw in August, and his ACTH was 45.6 pg/mL, instead of being in the high teens or low 20s as usual.

First Question:
The trainer's vet said to re-test Inky 6 months after he has been on pergolide without any disruptions. That would be February.  Would that be useful at that time of year?

Also, his insulin tested at 31.85 uIU/mL, which is higher than it has been in the past, altho it is still in the reference range. The trainer's vet has declined to test for glucose so I can't do the IR calculator.

Second Question:
Should I get my old vet out to test for insulin/glucose whether or not it makes sense to re-test ACTH in February? If so, does time of year matter? Inky overnights on pasture in summer and spends days in a dry lot. In the current season, he will spend 24/7 on dry lot with just round bale hay and his RSR beet pulp and alfalfa pellets.

Thank you for whatever guidance you can offer!

Karin & Inky

Forest, VA


July 27, 2015

Sherry Morse

Hi Karin,

You can retest anytime after the 3 week mark of being back on meds to see if the dose is correct.  Testing in February will be after the rise and tell you if the dose he is on is controlling his PPID when ACTH should be at its lowest.  While Inky's insulin is high without knowing the circumstances of the testing we can't really comment on it (how long after feeding, would it be fasting/non-fasting, when was he exercised, etc).