Page 941 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

916 CHAPTER 6

VetBooks.ir EQUINE METABOLIC SYNDROME Mustangs and Arabians. Those breeds may be more
metabolically efficient (‘easy-keepers’ and ‘good-
Other and previous names: peripheral Cushing’s
syndrome, prelaminitic metabolic syndrome, doers’) and therefore more likely to develop EMS.
Insulin dysregulation is a term used to describe
pasture-associated laminitis, insulin resistance syn- either insulin resistance or hyperinsulinaemia
drome, syndrome X, omental Cushing’s syndrome after an oral glucose load, while EMS describes
and central obesity. a horse with a specific set of clinical signs. Insulin
resistance is the inability to respond adequately to
Definition/overview insulin, whereas hyperinsulinaemia is the secre-
EMS is a collection of clinical signs and metabolic tion of an inappropriate amount of insulin after a
dysregulations leading to a predisposition toward carbohydrate stimulus. Horses with EMS usually
laminitis. Horses with EMS tend to be obese or have hyperinsulinaemia and insulin resistance but
overweight, have poor insulin/glucose regulation sometimes only one component of insulin dysregu-
and abnormal lipid metabolism. Laminitis is the lation is observed. Whether hyperinsulinaemia is a
main problem of horses with EMS but hyperlipae- compensatory effect of insulin resistance or insulin
mia, hypertension and subfertility are also features resistance is a consequence of chronic hyperinsu-
of the syndrome. With increased feed quality and linaemia is still not determined, but recent studies
decreased activity, EMS has become a major concern on the equine enteroinsular axis would suggest that
of the equine industry. EMS and PPID are two very hyperinsulinaemia could be an initiating factor. The
different, but not mutually exclusive entities, and detailed link between insulin and laminitis is unclear
they can coexist in the same animal. but insulin has many effects on epithelial cell func-
tion and proliferation that could potentially serve as
Aetiology/pathophysiology a trigger for laminitis.
The specific aetiology for EMS is currently unknown
but insulin dysregulation is central to the pathogen- Clinical presentation
esis of the syndrome. Although no specific genes have Horses are described as ‘easy-keepers’ and ‘good-
been clearly identified, a genetic predisposition is doers’, with thick, cresty necks and fat accumu-
very likely, since EMS is seen more commonly in cer- lation over their rumps and, if they are males, in
tain breeds including ponies, Morgans, Paso Finos, their sheaths (Figs. 6.12, 6.13). They tend to suffer

6.12 6.13

Figs. 6.12, 6.13 A horse with equine metabolic syndrome displaying a typical cresty neck and excessive fat
deposition around the tail head area.