So excessive peeing/polyuria is seen commonly in IR as well as PPID bc of the abnormally high glucose in blood (hyperglycemia).

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Horses rarely have high glucose levels. Finger can be pointed at high cortisol levels,though.

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Good point. But how does high cortisol result in PU/PD in IR-only horses (non-PPID)? Transient stress?

I guess b/c i check my mare's glucose & insulin so often (and she has been repeatedly hyperglycemic) that I was inclined to believe hyperglycemia was spurring the PU/PD. I check it with glucometer at draw and then send out G&I on same sample in a serum tube that isnt always spun right away. Subsequent lab results always show a markedly lowered BG from glucometer results in tubes not spun quickly (from known RBC consumption no doubt). I'm wondering if hyperglycemia isnt more common but undocumented in chronic IRs w severe hyperinsulinemia bc of the typical way ambulatory vets draw blood samples: a single serum tube that sits in the car for hours before getting spun. Its just something Ive been pondering bc I have the overlap with handling diabetic dog & cat blood w immed access to glucometers...but of course we're also talking two distinctly different diabetes mellitus: type I and type II...

Furthermore, my mare was diagnosed PPID shortly after the hyperglycemic episodes so i've sorta invalidated my own argument ;) but perhaps its a good experiment for my 8yo IR gelding with normal eACTH and no PPID symptoms

Sincerely,
Kerry in NY
Pinky Sept 2014
Tofurky Nov 2014