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Causes of Cushing's Disease in Dogs

By June 19, 2012 | See Comments

Causes of Cushing's Disease in Dogs

There are three types of Cushing’s disease; pituitary dependent, adrenal dependent, and iatrogenic Cushing’s. Learn their causes here.

Understanding the endocrine gland system of a dog is necessary to understanding Cushing’s disease. The endocrine system delivers messages, in the form of hormones, to every part of the dog, by means of the blood stream. The pituitary gland, located at the base of the dog’s brain, and the two adrenal glands, located near the kidneys, are the endocrine glands in charge of controlling the levels of cortisol. Cortisol is a hormone that helps maintain the homeostasis of the body, by converting protein into energy, improving fight or flight instinct, supporting the immune system, memory, and general coping with psychological and physiological stresses.

The pituitary gland produces the hormone adrenocorticotrophic (ACTH), which modulates the release of cortisol, by sending a message to the adrenal glands, about whether or not the body is under stress, and to what degree. The more stress, the more cortisol the adrenal glands are told to produce. This process is integral to the balance of the animal’s entire system. There are three types of Cushing’s disease; pituitary dependent, adrenal dependent, and iatrogenic Cushing’s.

Pituitary Dependent Cushing’s Disease

Pituitary dependent Cushing’s disease is caused by small tumors on the pituitary gland itself. These small tumors, known as microadenomas, prevent the pituitary gland from understanding that the blood cortisol levels are high. Therefore the adrenal glands continuously produce cortisol, effectively poisoning the blood.

Physically, a dog with pituitary dependent Cushing’s disease, tends to have very large adrenal glands, due to constant work. Occasionally, the tumors may metastasize to over one centimeter, and may cause other problems, such as blindness, not associated directly with Cushing’s disease.

Adrenal Dependent Cushing’s Disease

Adrenal dependent Cushing’s disease is caused by similar tumors to the pituitary dependent Cushing’s. However, they directly impede the cortisol level receptors. The adrenal gland no longer understands, or just ignores the information from the pituitary gland, pertaining to cortisol release. These tumors are adenomas, and half the time are benign, but the other half of the time they are malignant, or adenocarcinomas.

A dog with adrenal dependent Cushing’s disease typically has tumors on one adrenal gland, causing the overproduction of cortisol, resulting in enlargement. If the other adrenal gland remains free of tumors, it tends to shrink from underproduction to compensate. A dog with adrenal dependent Cushing's Disease might benefit from a medicine like Vetoryl.

Iatrogenic Cushing’s Disease

Iatrogenic Cushing’s is caused by extended exposure to powerful external steroids. If a dog suffers from chronic conditions, such as allergies, and is administered external steroids, such as prednisone, in high doses for an extended period of time, the adrenal glands can no longer control the hormone levels in the blood and then will atrophy.

A dog with iatrogenic Cushing’s disease typically has very small atrophied adrenal glands from lack of work.

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by,your veterinarian. Always seek the advice of your veterinarian or other qualified professional with any questions you may have regarding a medical condition. Never disregard or delay seeking professional advice due to what you may have read on our website.


My dog is a female dachshund almost 15 yrs, and had liver issues over past year. She is on royal canine hepatic dry food and marine plus. Last year she had symptoms of stroke but bounced back. Took her to neurologist but they said I can have MRI done to confirm but being she was so much better was afraid to put her under anesthesia to test. She has now had extreme high cortisol level, but low dose dex test came up negative. Vet feels may be false read, but due to her age and symptoms not as severe to be conservative at this time. I would do ultrasound if they can do without putting her under anesthesia. (waiting to here from vet) Here worst symptom is ravenous appetite and showing signs of weakness in back legs. I was wondering if anyone has had any benefits with flaxseed lignans and melatonin? I would do anything for my dog but I don't want to be too aggressive due to her age. Plus she isn't good with pain meds and anesthesia. The cushing meds seem so scary. My vet doesn't seem to into holistic treatments but said to do what I feel I need to. I am so overwhelmed by everything on line and don't know what to do. I did get flaxseed and melatonin. Started flaxseed but was concerned with melatonin. Any input would be so appreciated!

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