Gunner's TRH stimulation test is positive for PPID. His baseline ACTH is normal. I remember seeing a post by Dr. Kellon about figuring out a Pergolide dosage for horses with normal baseline ACTH but I cannot seem to find it. 
His plasma ACTH was 16 pg/ml pre TRH administration, 197 pg/ml at 10 min, and 58 pg/ml at 30 min. Both non-fasting insulin and leptin were within the range, 32.85 uIU/ml and 6.11 ng/ml respectively.

Thank you, as always, for the help!
--
Ed P in TX 2022
Atticus's Case History
Atticus's album
Gunner's Case History
Gunner's album

Hi Ed,
I think most horses start with a dose of 1 mg Prascend, pretreating with Advanced Protection Formula (APF) and titrating the dose up 0.25 mg every 4-5 days, to be cautious.  After three weeks, you can retest.  But here’s the catch.  TRH stim tests are only used for diagnosis and there are no standards for TRH stim testing after the horse starts pergolide.  Assumptions can be made from the general trend.  Why did you decide to test him for PPID?   Changes in those symptoms may be what you need to monitor to adjust his dose.
While the insulin value is safe, don’t get in the habit of calling it normal.  Midway in the range - about 25 in this case - is the goal to keep in mind.  When you retest his ACTH, be sure to do insulin and glucose as well.
--

Hi Ed,

For Gunner, you could try 0.5-1 mg pergolide starting in June for the seasonal rise only.  Redoing baseline--not Stim--ACTH (+ insulin, glucose, always) bloodwork at peak rise (late September in the northern hemisphere) is the best way to make sure your dose is effective, as well as monitoring the signs of PPID.  Now that Gunner has been diagnosed, keeping his ACTH in the teens to low 20s during peak rise is your goal.

Does Gunner display any visible signs of PPID?  If he does not, you should read this message thread.
Particularly Dr Kellon's posts. 

--
Kirsten and Shaku (EMS + PPID) and Snickers (EMS) - 2019
Kitimat, BC, Canada
ECIR Group Moderator
Shaku's Case History
Shaku's Photo Album

Snickers' Case History
Snickers' Photo Album

Sherry and Martha, thank you for your responses. I have a better idea of the target insulin readings from Sherry's other post now.

I'm still confused about the pergolide dosage though. I'm following the "Reading ACTH TRH Results" post, where the situation appears to be somewhat similar, except the horse is already on pergolide. A quote from Dr. Kellon: "The first question we have no answer for is what does a normal baseline ACTH and abnormal TRH response mean? Are all these horses going to progress to symptomatic PPID or does it just mean the pituitary is enlarged but not active unless artificially stimulated? I suspect both scenarios are possible so that means you have to look for clinical signs specific to PPID. Did she have any? If so, have they improved?"

Well, in Gunner's case the only clinical sign was weight gain and a small crest developing last spring, and also elevated insulin (which may be unrelated to ACTH). Both conditions improved: he's now on the skinny side, maybe even a little underweight, there is no crest left at all, and his insulin is still elevated, but much better than it was, down to 32 from 67. Should he be on pergolide at all? My understanding is that a positive TRH stimulation test indicates that dopaminergic regulation of the pituitary is compromised. Will dopamine agonist like pergolide protect the pituitary from further hyperplasia? Will it potentially also protect from negative effects of increased cortisol in the presence of any potential stressors if downregulation of ACTH is compromised? Conversely, should I wait with pergolide but try other ways to modulate/potentiate dopamine while monitoring his ACTH? Is trying to supplement with tyrosine a good idea? Could a vitex supplement help? Adaptogens?

I'm sorry for asking so many questions. I'm just trying to figure out a plan for him.

Thanks!

--
Ed P in TX 2022
Atticus's Case History
Atticus's album
Gunner's Case History
Gunner's album

I honestly can’t answer most of your questions, Ed, but I can address a few things.  I know that excess weight is on the list of symptoms for PPID but that has not been my experience.  Excess weight, fat pads and crests, I associate with IR.  Maybe there’s another stage of the disease I’ve missed but I wouldn’t suspect PPID on the basis of those observations.

And I’m confused about what you don’t understand about pergolide dosages.  The correct dose is the one that controls ACTH.  However, my experience has been that in some cases higher doses than that are better.  I make that determination based on symptoms such as polyuria.  The PPID in my five critters seems well controlled so I’m not concerned that it might be affecting their insulin.  Maybe if you phrased your concern a bit differently, I would “get” it or someone else might instead.

There’s been some discussion about the tumor possibly being more likely to stabilize or even regress with correct pergolide management of the PPID so that’s a goal we promote.  Vitex will control some PPID symptoms although not ACTH levels and it’s advised not to give it once you start a horse on pergolide.  Quite a few years ago, I had all these middle aged horses on CTB as a result of someone’s recommendation.  They all progressed to need pergolide so I joked that the CTB was the cause.  It helps the horse to drop a seasonal coat, which pergolide often doesn’t.  

If I had concerns about whether or not my horse needed pergolide, I would plan to have him on a low dose from mid June to mid December and then remove it and retest in the late winter or early spring.
--