ACTH and Insulin numbers during the Seasonal rise


Dr. Kellon, I have a question about insulin and ACTH numbers, from blood drawn a week ago and sent to Cornell. Haven't seen the actual lab report yet.

Vet told client that her mare, who had been sore-footed last month -- she's a very chubby and cresty 12 y.o. Arabian X, was not IR nor PPID by bloodwork.

Justification was this finding: "all the numbers were 'high normal'" and vet said specifically about the ACTH, something along the lines of “we think that 2 x the normal (40 at this time of year) is perfectly acceptable, so an ACTH of 100 is fine and doesn’t need treatment with pergolide.” 
Can you shed some light on this reasoning?


Jannalee Smithey, EDO
Talent, Oregon
Board of Directors
ECIR Group, Inc.
Joined 2008

Eleanor Kellon, VMD

Most if not all labs now have seasonally adjusted reference ranges for ACTH. That means they are already corrected for the time of year and you don't have to make any further adjustments. I would agree that with older horses (20+) the cutoffs may be too low but not for a 12 YO.

As we have discussed several times here recently, the situation with insulin is even worse. Lab ranges are not normals. They are the values seen in animals they tested under the feeding conditions those animals had. This may have nothing to do with feeding hay only night before and day of testing, like we do. The "normals" used in our calculator are taken from the VA Polytechnic study of ponies at pasture - which included both normal and EMS ponies.
Eleanor in PA  2 for 1 course sale
EC Owner 2001