By Dr. Patrick Mahaney, VMD
Cushing's disease is a common endocrine (glandular) problem seen and middle-aged to older dogs. Also known as hyperadrenocorticism, the condition is caused by excessive corticosteroid production by the adrenal glands. The most common cause of canine Cushing's disease is the presence of a benign tumor in the pituitary gland, which releases hormones that stimulate the adrenal glands’ production of corticosteroids. Less frequently, a corticosteroid-producing tumor can grow on one or both of the adrenal glands.
Dogs being treated with oral or injectable corticosteroids (prednisone, dexamethasone, etc.) can also exhibits clinical signs of Cushing's disease. Therefore, it’s important that a veterinarian consider all factors potentially contributing to clinical signs of hyperadrenocorticism.
Corticosteroids cause mild to significant increases in water needs and consumption. Some dogs may feel impelled to drink any water they find. Therefore, it's crucial to have plenty of fresh water available so that water that may possibly be contaminated with bacteria, viruses, parasites, or toxins are less likely to be sought to meet increased daily water requirements. Additionally, providing fresh, moist foods can help meet hydration needs so that questionable water sources are not consumed.
When more water is consumed, there’s an associated increase in the quantity of urine produced. Not only can you see your dog produce larger volumes of urine, but urinary frequency also increases. Dogs may inappropriately urinate inside the home or leak urine from the penis or vulva while sleeping. Urine is commonly more dilute as a result of increased water consumption and may appear lighter-yellow or even clear.
Cushingoid dogs are commonly hungry. Therefore, they are interested in eating larger and more frequent volumes of food and treats. Additionally, dietary indiscretion (eating something one should not) can be seen. Consumption of environmental substances like dirt, grass, rocks, feces, wood, metal, etc., known as Pica, can have severe health consequences, and should be expected and prevented through measures taken by owners of dogs that have Cushing’s disease.
Increased respiratory rate is a very common clinical sign of Cushing's disease. Panting can occur despite being in a cool and comfortable environment. This type of heavy breathing may prevent your dog from resting properly during daytime naps and while sleeping overnight.
Cushing’s disease leads to body composition changes, including abdominal distention and muscle atrophy. The abdomen takes on a pot-bellied appearance, which is primarily due to steroid-associated liver enlargement (steroids for inflammation are a common treatment for Cushing’s) while the vertebral column (backbone) and other bony areas appear more prominent due loss of muscle mass.
Thinning hair and skin, chronic or unusual infections (bacteria, yeast, mange, etc.), the development of blackheads, and a darkened-appearance to the skin (especially on the abdomen) are all associated with Cushing's disease.
Aggression, increased pursuance of food and water, exercise intolerance, lethargy, and difficulty moving around in their day-to-day environments (navigating stairs, going up onto elevated surfaces, etc.) are some of the behavior changes commonly seen in dogs afflicted by Cushing’s disease.