When Hormones Go Haywire

Disorders of the endocrine system — the body’s hormone-producing glands — can result in ongoing health issues and a high risk of laminitis. Edd Knowles MRCVS and Andy Durham MRCVS discuss the latest findings.

- Edd Knowles & Andy Durham

IN the past few years, there has been a huge growth in research into equine hormonal disease, something we now commonly recognise in both horses and ponies in the UK.

Researchers from around the world gathered earlier this year at the Havemeyer Foundation International Summit in Florida, USA, to discuss their progress, shedding valuable light on the cause and treatment of these complex conditions.

There are two common hormonal (or endocrine) conditions that affect horses: PPID (pituitary pars intermedia dysfunction, also known as Cushing’s disease) and EMS (equine metabolic syndrome). The conditions share some similarities and both have links with laminitis, but there are also important differences between them.

PPID usually occurs in ageing horses, especially from the mid-teens onwards, although younger cases are recognised. The pituitary gland, found dangling just below the brain, produces a range of different hormones that work as messengers in the body, controlling different processes such as growth, breeding cycles and response to stress. When PPID develops, part of the pituitary gland becomes overactive and produces too many hormones.

Signs of PPID can vary, ranging from abnormal hair growth or delayed coat shedding to muscle loss, excessive drinking and urinating, laminitis, lack of energy and recurring infections. We can all spot the telltale signs of severe, advanced PPID — the long curly coat and the pot belly, but vets often use blood tests to identify PPID in horses with more subtle signs. Accurate diagnosis is important, because some of these issues could also be caused by other conditions.