Pituitary pars intermedia dysfunction (PPID) of horses, commonly known as Cushing’s Syndrome is gaining more and more attention, and that’s because it is becoming more common. Affecting usually older horses, with a predisposition for certain breeds, such as ponies, huge sums of money have been spent on the pathology, the symptoms, and on treatment. The long, curly coats and predisposition to laminitis and secondary infections make identification of the disorder relatively easy.

I was never told about Cushing’s in horses when I was in veterinary school before 1956 when I graduated. I had never seen or heard of a case.

The veterinarians prior to the 20th century were keen observers. If a horse suddenly grew a long curly coat, they couldn’t have missed it.

So when, after 1960, I started to see cases (including two of my own ponies) I researched the literature. I found only one reported case, by a German army veterinarian in 1942.

If a similar condition suddenly appeared and became an increasingly common problem in humans, or in dogs, it would excite a lot of curiosity. What is causing it?

So much time, money, and skill has been spent on understanding and treating Cushing’s in horses, but, WHY has it appeared since the mid 20th century, why is it increasing, and what is causing it?

One theory is that horses are living longer and we are therefore seeing more cases. I don’t buy it. The research method is to survey populations elsewhere in the world. Does it occur in more primitive societies? Has it been identified in feral and wild horse populations such as American mustangs and Australian Brumbies?

Medically, prevention of disease surpasses cure.

What I suspect is an environmental cause. Why so few cases prior to World War II? Why is the incidence increasing? What other species is the PPID so common in? If not, why not?

Equine Cushing’s is being reported as a common disorder of aging horses. If so, why was it not described in past centuries? It is a very noticeable disease. Treatment is a desirable goal, but let’s work on the etiology (cause). It is too common to be part of the normal aging process, and it is increasing.