Re: Effect of elevated ACTH on Insulin
I'm sure others will chime in, but here's my 2¢ worth:
1- There is no direct correlation between ACTH & Insulin levels in the sense that you could say "if ACTH rises 10 pg/mL the Insulin will rise 100 uIU/mL" on the other hand it is well established through the experiences of the 10,000 members of this group that uncontrolled ACTH does drive Insulin numbers.
The fact that your horse tested low normal for Leptin tells me that it is not genetically caused IR and that the high Insulin is being driven by uncontrolled PPID.
2- Yes, you should start him on Pergolide ASAP, Prascend if you have no other choice, though compounded Pergolide is just as effective and a lot cheaper. Also it is easier to tailor the dose using compounded Pergolide in capsules, you can have them made up in virtually any dosage. Start him on 0.25mg of Pergolide for 4 days then increase the dose to 0.50mg for 4 days, then increase to 0.75mg for 4 days, then increase to 1mg and hold for 10 days then retest ACTH, at this time of year it should be below 47 pg/mL if it is still above that increase the dose to 2mg in the same manner you reached 1mg. Keep doing this cycle until the ACTH is controlled. I prefer to administer the dose once per day in the evening and with the dose this small splitting it makes no sense.
3- Yes, once the ACTH is normal and the PPID controlled his Insulin should return to normal.
4) Yes, treat his PPID with the correct dose of Pergolide (the correct dose is the lowest dose which controls his ACTH levels and symptoms) , make sure his diet is tightly controlled and balanced and support his immune system nutritionally. The exercise program is excellent, as long as he is not laminitic, and will help control normal IR, but you can run the legs of a horse whose Insulin is elevated due to uncontrolled PPID and never control his IR unless the horse is getting the correct dose of Pergolide as well.
George & Wind
Mica Bay, ON