Hi Robyn

I presume you had Paddy's blood tested at Cambridge - The Hormone Lab?

I have queried their ACTH normal range before. According to their website they use RIA (radioimmunoassay), as do most labs testing equine ACTH. I don't remember seeing any/many (?) labs with a normal range in excess of 47 pg/ml - Liphook's range for Aug-Oct. And nearly all the labs I've seen used for ACTH testing have a normal range of around <35 pg/mg - other than those that now adjust for the seasonal rise.

See p27-28 of their lab manual for ACTH & insulin testing:
http://thehormonelab.com/core/..uploads/csls/Lab-Service-Information-Manual-March-2011.pdf
"However very high levels (>300pg/mL) are still highly suggestive of ECS and a normal level in the autumn (<100 pg/mL) is more likely to be truly negative."

Is it possible for normal ranges to differ this much??

If not, then yes without a doubt Paddy's ACTH is far too high, and I would increase his pergolide - you don't even know how high his ACTH actually is, it could be far higher than 600 pg/ml. Andy Durham said in his Aug Prascend webinar that horses need different doses of pergolide and he has horses on anything from 1-2 mg/day to 8 mg/day. The correct dose is the dose that controls the clinical symptoms and the ACTH.

For this reason I always recommend that people in the UK ask to have their blood tested at Liphook - not only are Liphook doing a lot of research into endocrine testing, but their results are in line with most of the other good labs recommended by this group.

I would also say that his insulin is above normal - I believe it has been mentioned on here that some labs in the USA have results approx. 2 x higher than Cornell, so perhaps this is similar with Cambridge. But nonetheless you are looking for an insulin result <20 uIU/ml according to most vets, and ideally <10 uIU/ml. And his glucose is right at the top of the normal range given, and over 100 mg/dl.

Cortisol isn't considered diagnostic of PPID by most vets.

I'd be grateful if someone with more knowledge than me could comment on the ACTH normal range mentioned above - I'm currently researching this but it's taking a while. If no one has an answer, I'll contact the lab next week and see what I can find out.

Andrea
UK/France Jan 2010
www.thelaminitissite.org