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Cushing’s Disease in Dogs: Most Important Information for Dog Owners

Cushing’s disease in dogs is also known as Hyperadrenocorticism or Hypercortisolism. The disease is associated with excessive production or administration of glucocorticoids and is one of the most commonly diagnosed endocrinopathies in dogs. It is a condition that a tumor may cause in the pituitary gland. The treatment is an expensive and ongoing process, and the disease needs proper monitoring. Hyperadrenocorticism is rare in the cat.

Important Information About Cushing’s Disease in Dogs

Cushing’s disease is a metabolic and endocrine disorder of dogs. When your dog falls on Cushing’s syndrome that time your dog’s body produces more of a hormone called cortisol. Cortisol helps them respond to control their weight, stress, fight infection, and keep their blood sugar levels in check. But when it produces too much or too little of it may cause some troubles.

Miniature Poodle

Dog Breeds Prone to Cushing’s Disease

Any breeds of dog can develop hyperadrenocorticism, but breeds that are more prone to Cushing’s disease include-

  • Poodles, especially miniature poodles.
  • Dachshunds.
  • Yorkshire Terrier.
  • Jack Russell Terrier.
  • Staffordshire Bull Terrier.
  • Boston Terriers.
  • Boxers.

What Causes Cushing’s Disease in Dogs?

Cushing’s disease can be iatrogenic or spontaneous. Spontaneously occurring Cushing’s disease may be associated with inappropriate secretion of ACTH by the pituitary or associated with a primary adrenal disorder.

Types of Hyperadrenocorticism in Dog

  • Pituitary-dependent Hyperadrenocorticism (PDH)– PDH is a disease of middle-aged to older dogs, with an age range of 2-16 years and a middle-age of 7-9 years.
  • Adrenal-dependent Hyperadrenocorticism (ADH)– Dogs with adrenal-dependant hyperadrenocorticism tend to be older with a range of 6-16 years and a middle-age of 10-11 years.

There is no significant variation in sex distribution in PDH. However, female dogs are thrice more likely to develop adrenal tumors than males. In addition, affected dogs usually develop a classic combination of clinical signs associated with increased glucocorticoid levels.

Another kind called iatrogenic Cushing’s syndrome occurs after a dog has taken steroids for a long time.

Cushing’s Disease in Dogs Symptoms

The common signs and symptoms of Cushing’s disease are as follows:

  • Polydipsia (drinking more water than usual).
  • Polyuria (increase volume f urine and frequency).
  • Polyphagia (eating more food than average).
  • Abdominal distension and pain.
  • Liver enlargement (hepatomegaly).
  • Muscle wasting.
  • Muscle weakness.
  • Lethargy.
  • Poor exercise tolerance.
  • Skin change becomes rough and irregular.
  • Alopecia (loss of hair in different parts of the body).
  • Persistent anoestrous in females.
  •  Testicular atrophy in male dogs.
  • Calcinosis cutis.
  • Myotonia.
  • Neurologic disorders.
  • Gets a pot belly appearance.
  • Thinning of the skin.

Diagnosis of Cushing’s Disease in Dogs

There is no 100% accurate diagnosing procedure for your dog’s hyperadrenocorticism. Your veterinarian will start diagnosis based on signs, and the confirmatory diagnosis performed a few tests on laboratory findings. The vet will do a physical examination, routine laboratory tests, and radiographic findings, but your experts confirmed the disease by ACTH stimulation test or a low-dose dexamethasone suppression test.

Radiographs examination of the thorax and abdomen is advisable in all cases of suspected or proven Cushing’s. Although positive diagnostic information is only received in the small number of cases in which adrenal enlargement can be found, the number and frequency of radiologic changes consistent with hyperadrenocorticism provide a valuable aid to diagnosis. All of the above are common in dogs with Hyperadrenocorticism. Your veterinarian will follow up with a hormone screening test, such as;

ACTH Stimulation Test

The ACTH stimulation test is the best diagnostic test for distinguishing spontaneously from iatrogenic hyperadrenocorticism. It reliably identifies more than 50% of dogs with adrenal-dependent Cushing’s disease and about 85% of dogs with PDH.

Plasma ACTH Concentration

Dogs with adrenal tumors have low endogenous ACTH concentrations, whereas cases of PDH have a high standard or high concentrations.

Diagnostic Imaging and Radiology

Diagnostic imaging techniques, particularly USG of the abdominal region, have also proved sensitive in distinguishing animals with PDH from adrenocortical tumors.

High-Dose Dexamethasone Suppression Test

It is the most commonly used test for differentiating the cause of Cushing’s disease, but it is less accurate than abdominal ultrasonography or plasma ACTH measurements. Therefore, this test is indicated in those cases where a screening test has established the diagnosis of hyperadrenocorticism. Still, the differentiation of adrenal-dependent and PDH has not been determined. The pituitary ACTH secretion is inhibited by the negative feedback of high doses of dexamethasone, thus suppressing serum cortisol amount by 50% or more by four hours. However, adrenocortical tumors are autonomous, and thus serum cortisol is not suppressed at four hours.  

Differential Diagnosis of Cushing’s Disease

The disease must be differentiated from the following diseases:

Treating Cushing’s Disease in Dogs

The most common drug Mitotane is the older drug that vets don’t choose much anymore for PDH. Mitotane was discovered to have adrenocorticolytic effects before it was used as an insecticide. It selectively destroys the zona fasciculate and zona reticularis while tending to preserve the zona glomerulosa. Mitotane therapy your veterinarian should prescribe only the diagnosis of hyperthyroidism has been confirmed. It should never be used empirically because of its rapid action.

Ketoconazole has a reversible inhibitory effect on glucocorticoid synthesis while having minimal effects on mineralocorticoid production. Your vets have been used Ketoconazole effectively to control hyperadrenocorticism in dogs, but it is not effective in cats. Unfortunately, however, Ketoconazole is not uniformly efficacious in dogs, and between one-third to one-half of all dogs treated fail to respond adequately.

Dogs diagnosed as having adrenal-dependent hypoadrenocorticism carry the best prognosis if the tumor can be removed surgically, although your vet also recommends mitotane therapy. The technique is sensitive using the paracostal flank approach. Your experienced surgeons should perform it as the perioperative mortality is high. Postoperative mortality is essential as the contralateral adrenal cortex will be atrophic and unable to respond to the stress.

What is the prognosis of Cushing’s Disease in Dogs?

Although neither medical treatment can cure a dog with Cushing’s disease, control is possible for many years if the tumor is small. If the tumor is large and it affects the brain, the dogs have a less favorable prognosis. The prognosis for your pets diagnosed with malignant adrenal tumors is guarded to poor. In the case of benign adrenal tumors, however, surgery is usually curative.

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