"Cushinoid syndrome horse?"

["guest@endurance.net" <guest@endurance.net>]

Patty Lambert esppatty@juno.com
One of my horses, age 20, has recently been tested and found to 
have an insulin level ten times normal in his blood. He has not 
been comfortable for about the past year, seeming to have ouchy 
feet but no obvious cause (no heat, no unusual pulse, no "founder rings"). 
The (new) vet says he has chronic low-level laminitis (has some 
mild rotation in all 4 feet), which is a symptom of Cushings. 
Last year, however, he was tested for Cushings and thyroid and 
found to be normal, although his insulin level was high then as 
well. Since he has none of the other classic Cushings signs 
(shaggy coat that won't shed, pot belly,excessive 
thirst/urination), I am wondering if he could be diabetic or 
something else. I feed him straight oats with brewers yeast and 
antioxidants. I limit his pasture to keep him from getting 
overweight.For the past 2 weeks,he has been on cyproheptadine, 
and I think I see some improvement. 
My question is: has anyone out there had a similar experience 
with high insulin levels, and what was the diagnosis/treatment, 
and any suggestions?? Thanks.   Patty & Frosty