For years, vets and researchers have recognised a seasonal influence on the pituitary gland in equine Cushing’s disease cases and normal horses. This seasonal influence is the reason why we have seasonal (or in Liphook’s case, weekly) adjusted reference intervals for basal ACTH testing. The seasonal influence on the pituitary gland also impacts on our interpretation of follow-up tests when starting or monitoring a horse on pergolide therapy. Check out this latest podcast where Victoria South and Andy Durham discuss a variety of PPID scenarios that many of us are facing at this time of year.
Here's a link to the Equine Endocrinology Group's website which great free-to-download summary documents on PPID and EMS: http://sites.tufts.edu/equineendogroup/
Abstracts from the latest Equine Endocrinology Havemeyer Summit -including the TRH stim test reference intervals abstract - can be found here: https://sites.tufts.edu/equineendogroup/files/2017/01/2017-Equine-Endocrinology-Summit-D-Russell-Havemeyer-Foundation.pdf