Cushings Disease in dogs is the overproduction of the hormone, glucocorticoid, by the adrenal glands. This is also referred to as canine hyperadrenocorticism. Cushings disease in dogs is a common condition that primarily affects middle aged dogs around 8 to 12 years old. Female dogs are at higher risk of developing Cushings disease than male dogs. High glucocorticoid level in the blood would result to increased blood glucose levels, gastrointestinal irritation due to amplified gastric acid and pepsin production, and increased suppression of the immune system.
What are the 2 forms of Cushings Disease in dogs?
Cushings disease in dogs has two forms, namely, the Pituitary dependent and the Adrenal dependent. Pituitary dependent Cushings disease in dogs occurs when there is an abnormality in the pituitary gland causing the overproduction of the glucocorticoids. The pituitary gland may be affected by a tumor that even if the body no longer needs glucocorticoids, the pituitary gland would still stimulate the adrenal cortex to produce more glucocorticoids.
On the other hand, Adrenal dependent Cushings disease in dogs happens when the adrenal gland is affected with tumor or other abnormalities causing the increased production of glucocorticoids. Even if the pituitary gland stops the stimulation of the adrenal gland to produce glucocorticoids, the adrenal gland would not heed and still continues to produce the hormone.
What are the predisposing factors that lead to Cushings disease in dogs?
There are different factors that can cause Cushings disease in dogs. These are the following:
- Increased secretion by the pituitary gland of the adrenocorticotropic hormone causing the increased release by the adrenal glands, specifically the adrenal cortex, of glucocorticoids even if the body does not need it anymore.
- Pituitary adenoma or adrenal adenoma causing increased production of glucocorticoids.
- Prolonged therapy using steroids may cause internal changes in the dog’s body that can alter the production of glucocorticoids.
What are the signs and symptoms of Cushings disease in dogs?
The signs and symptoms of Cushings disease in dogs can be experienced differently and observed gradually. Since the symptoms can also be observed in other conditions, consultation with the veterinarian to properly diagnose the disease should be done.
Below are the signs and symptoms of Cushings disease in dogs:
- The dog may experience signs of hyperglycemia such as increased urination or polyuria, increased interest in food and eating or polyphagia and increased water consumption or polydipsia.
- Pot belly appearance
- The head is too lean that it adapts a skull-like appearance.
- The dog may experience reduced weight because of the loss of muscle mass; or weight gain because of the distribution of fats.
- Generalized weakness
- Alopecia or baldness
- Observable panting
- Low resistance to infection due to overproduction of glucocorticoids
- Wounds heal slowly
- Seizures may happen anytime
- Calcinosis cutis or calcified bulge in the skin
How is Cushings disease in dogs diagnosed?
The following are means to correctly find out if Cushing Disease is indeed the problem.
- Adrenocorticotropic Hormone (ACTH) stimulation test
ACTH is the hormone responsible for the production of glucocorticoids. Blood is extracted from the dog for baseline data. After the extraction, the ACTH will be injected. Within 1 to 2 hours, the dog’s blood will be extracted again to measure the glucocorticoid level. However, the test cannot determine which form of the disease has affected the dog. The test is done with dexamethasone suppression to determine if there is still overproduction of glucocorticoids despite the suppression given to the dog.
- Low dose and high dose Dexamethasone Suppression Test
This is considered the most appropriate test for Cushings disease in dogs. Blood is extracted from the dog for baseline data. In low dose dexamethasone suppression test, a low amount of dexamethasone is injected into the dog then a blood sample is taken after 4 to 8 hours of administration. Cushings disease is confirmed when the dog’s blood glucocorticoid levels is still high despite the presence of dexamethasone. Low dose dexamethasone suppression test does not determine which form of Cushings disease has affected the dog.
In high dose dexamethasone suppression test, high dose of dexamethasone is injected into the dog. Then 4 to 8 hours later, a blood sample would be taken. Unlike the low dose test, the high dose dexamethasone suppression test can determine which form of the disease the dog is suffering from. If it is adrenal dependent, the adrenal glands would not respond to the dexamethasone; while if it is pituitary dependent, pituitary gland would respond to the high dose dexamethasone given.
Cushings disease in dogs needs lifetime treatment. As long as the dog is still alive, the medication to control glucocorticoids level should be given. If the pet owner notices some changes in the dog’s behavior as well as health, a visit to the veterinarian should not be delayed so that the correct diagnosis and the proper treatment can be made right away.