The most common clinical signs of Cushing’s is an excessively long hair coat, which often fails to shed out in the warmer months. Other clinical signs include: weight loss, lethargy or poor performance, laminitis, increased water intake and urination, increased sweating, and mares may fail to cycle. The onset of these clinical signs is usually gradual over a year or more, but can also develop rapidly.

There are a number of illnesses and complications that can affect a newborn foal, such as; failure of passive transfer, septicemia, neonatal isoerythrolysis, musculoskeletal disorders, and the condition referred to as peripartum asphyxia syndrome.