Putting a brake on degeneration

Cushing’s disease is one of the most common illnesses in horses older than 15, but is your own horse or pony at risk? Gil Riley MRCVS investigates

- Gil Riley

CUSHING’S disease — also known as pituitary pars intermedia dysfunction (PPID) — is a progressive disorder caused by a dysfunction of the pituitary gland. This gland is located at the base of the brain and it produces an assortment of hormones.

In a horse with Cushing’s, the middle lobe of his pituitary gland becomes enlarged over time, often referred to as an adenoma, and results in the over-production of these hormones. The growth can compress the adjacent structures in the pituitary and hypothalamus – a region of the brain – resulting in loss of their function.

One of the hormones produced in the pars intermedia is the adrenocorticotrophic hormone (ACTH), which stimulates the cortex of the adrenal glands (two glands located close to the kidneys) to produce cortisol. An increase in ATCH production from the dysfunctional pituitary leads directly to an increase of cortisol circulating in the body.