What is Equine Cushing's disease? 
Cushing's disease is a degenerative disease of the brain stem. The hormonal consequences of this are mainly the overproduction of cortisone from the adrenal gland. Although this is the common consequence in most cases, it is by no means the only change that occurs. The main target organ for the condition is the pituitary gland. The gland becomes very active and can enlarge significantly - this is sometimes viewed as a tumour. The hormones produced by the overactive pituitary gland causes the adrenal gland to become overactive.
How do I know if my horse has Cushing's disease?
The most obvious sign is the characteristic long, curly coat (hirsutism). Over a number of years variations in the coat length and density develop. There may be variations in natural spring shedding and in some cases, spring molting does not take place at all. The coat becomes very dense, long and curly. Sweating is a common event and the coat often feels damp. Sweating is a result of warmth from an excessively thick, long coat and some of the hormonal changes and the pressure on the base of the brain where the thermoregulatory centres are located. 
How will my vet treat my horse?
There are no cures for Cushing's in horses. There are however useful drugs and some management procedures that will help significantly. Probably the nursing aspects are the most important - reliance on drugs is usually insufficient. Clipping of the coat and regular dental and farrier attention will help. Careful and regular worming and early detection of infections is essential. Checks on the body weight and general health are very helpful but need to be regularly carried out. Most feed merchants will be able to provide useful nutritional guidance for the older horse and a well nourished, well maintained horse may live for many years with the disease.