Canine Cushing’s disease is caused by an endocrine dysfunction and is mainly seen in middle- aged and older dogs. Although both are endocrine disorders and refer to high levels of cortisol in the blood, there is a mild difference between Cushing’s syndrome and Cushing’s disease in dogs. The difference basically lies in the factor that disturbs the production of cortisol, an adrenal-cortex hormone.
Cushing’s disease was first described in 1932 by Harvey Cushing, an American endocrinologist. Cortisol is an adrenal-cortex hormone, but its production is controlled by another endocrine gland, the pituitary gland. The disruption in the production of cortisol can be caused due to a problem with the adrenal gland or the pituitary gland.
Cushing’s disease specifically refers to pituitary adenoma (a benign tumor in the gland). The tumor interrupts the pituitary response to negative feedback to high cortisol levels. This means that despite adequate levels, the pituitary does not restrict the release of ACTH, a hormone that stimulates the adrenal cortex to release cortisol.
Cortisol is a glucocorticoid agent that plays an important role in the metabolism of proteins and carbohydrates. A high concentration of cortisol in the blood also exhibits mineralocorticoid activity, which impacts the metabolism of sodium, potassium. It also affects water levels in the body. Excessive cortisol thus leads to a combination of symptoms, including:
- Increased water consumption, which in turn leads to excessive urination.
- Increase in appetite and consumption, with visible enlargement of the abdomen. This occurs to such an extent that the dog may start getting into garbage and may also become overprotective of his food.
- Excessive hair loss, the number one reason for dog owners to consult a vet for getting the condition evaluated. It is mostly accompanied by a thin and brittle skin.
A series of tests may be performed to diagnose Cushing’s disease and to establish whether the condition exists due to an adrenal problem or a pituitary condition. The tests performed are:
- Checking ratios of urine cortisol and creatinine.
- Low or high dose dexamethasone suppression test.
- ACTH stimulation test.
- Abdominal ultrasound.
However, as there are certain conventional oral drugs that can influence both the adrenal and pituitary glands, many veterinarians refrain from specific laboratory procedures to determine which gland is affected.
As a pituitary tumor is a common cause behind Cushing’s disease, surgical excision is another option that may be considered. Surgical removal, however, depends upon whether the surgeon has the necessary skills to remove the gland. Another option that deserves looking at is homeopathic and/or herbal treatment of Cushing’s disease.