Equine Science Update

Hormonal disturbance (endocrinopathy) appears to be a common underlying cause of laminitis according to research from Finland.

The study, conducted between April 2007 and August 2008 at Helsinki University Equine Teaching Hospital, looked for signs of endocrinopathy in all cases of laminitis presented for examination. Almost 90% of horses with laminitis had endocrine abnormalities.

Hyperinsulinaemia, associated with obesity was the most common cause, accounting for two thirds of all cases of endocrinopathic laminitis.  Cushing’s disease (or Pituitary Pars Intermedia Dysfunction: PPID) was responsible for a third of the endocrine-associated laminitis cases.

Dr Ninja Karikoski and colleagues examined 36 horses and ponies with laminitis. Thirty-two of them (89%) had signs of endocrinopathy.

A full report of the  research has been published in the journal Domestic Animal Endocrinopathy.

Eleven horses had signs of PPID - hirsutism (long curly coat) and increased basal ACTH concentration or typical response to a dexamethasone suppression test.

Twenty-one horses had raised basal levels of insulin in the blood without signs of hirsutism.  All but one of these hyperinsulinaemic horses were overweight. Twelve had a body condition score (BCS) of four, (on a scale from zero to five, where five is obese) and eight had BCS of five.

In fact, the authors point out that even more animals may have had underlying hormonal disturbances, as the tests used to identify them may not have detected all cases. For example, hormone testing to diagnose PPID was only carried out on those horses showing hirsutism. So horses with PPID that did not have hirsutism might not have been identified.

Again, some cases of insulin resistance might have been missed because measuring basal insulin is less sensitive than using dynamic tests for diagnosing the condition.

The researchers also grouped the laminitic horses according to type and compared them with other cases seen at the hospital over the same period to see if the risk of laminitis differed between breeds. Horses were placed in four groups: warmblood horses; ponies; coldblood and Icelandic horses; and other light breeds - such as Standardbred, Arabian, and Quarter Horse. The data showed that ponies were significantly more likely than were other groups to get laminitis associated with an underlying endocrinopathy .

The researchers conclude that, in this study, most cases of laminitis were associated with an underlying hormonal disturbance.

They suggest that endocrine testing should be performed on all cases of laminitis unless there is a clear inflammatory or gastrointestinal cause.




For more details see:

The prevalence of endocrinopathic laminitis among horses presented for laminitis at a first-opinion/referral equine hospital.
NP Karikoski, I Horn, TW McGowan, CM McGowan
Domestic Animal Endocrinopathy (2011) 41, 111 - 117