Cushings disease or Hyperadrenocorticism is a complex disease with a rather complex history. It has been described initially in humans, but is not uncommon in our canine companions.
The name “Cushings disease” was coined by Mr Harvey Cushing who first described the collection of clinical symptoms seen from an over production of cortisol. He documented this in 1912 after being presented with an unusual set of symptoms in a female human patient in 1910. This patient by the name of Minnie presented with pain, obesity, abnormal hair growth, headaches and an underdevelopment of sexual characteristics. Cushing suggested that these signs were related to a pituitary tumour and showed some similarities to those with adrenal tumours.
Experimental evidence and case reports were compiled leading to Cushing’s publication in 1932, officially naming the pituitary gland as the underlying cause of ‘Cushing’s disease’. Further investigation over the years found links between the pituitary and adrenal glands. It was noted that clinical signs were similar for those with both pituitary and adrenal tumours. In truth, the phrase “Cushing’s disease” really only refers to the pituitary issue, however in veterinary medicine we use the phrases “hyperadrenocorticism” and “Cushings disease” interchangeably.
Hyperadrenocorticism refers to the overproduction of cortisol which is produced by the adrenal gland. As with a lot of our hormone production, it can get quite complicated as it is controlled quite tightly by complex mechanisms. The basic outline is as follows: The pituitary gland secretes hormone that stimulates the adrenal gland to produce its hormone. The pituitary gland and adrenal gland both are under the influence of feedback from the body so that this is regulated within a normal range. When delving deeper it can get quite complex!
This physiology means that both a problem with overstimulation of the adrenal gland by the pituitary, or an excessive production primarily by the adrenal gland can result in the clinical signs we see in hyperadrenocorticism. Given that cortisol has a large variety of impacts on the body, the increase within an individual can result in varied clinical signs. Commonly we see excessive thirst and appetite, a pot belly, muscle wastage and weakening, as well as liver enlargement and a thinning of the coat.
We tend to classify our patients into one of three categories; Primary (adrenal dependent), Secondary (pituitary dependent) or Iatrogenic (because of external intake of cortisol such as long term use of certain drugs). The later can be often be resolved after withdrawal of the drug.
As Veterinarians we see the disease more commonly in smaller dogs (less than 10kg) and they usually suffer from pituitary dependent disease. Larger breeds are less likely to suffer from the disease and if they do, adrenal disease is seen more often.
Diagnosis of hyperadrenocorticism is not clear cut and it combines the Vet to look at clinical signs, blood tests and often abdominal ultrasound images. There is no one test that gives us a yes or no answer.
Management of primary and secondary hyperadrenocorticism may be medical or surgical. In some cases where clinical signs are mild, we may elect to just monitor the patient until clinical signs are interrupting quality of life. It has been noted that treatment doesn’t often alter the longevity of the patient as mostly the adrenal and pituitary tumours are benign.
Surgical treatment is only really appropriate for adrenal disease and is a difficult procedure generally performed by a specialist trained surgeon. Surgical treatment is often curative as generally only one of the two adrenal glands are affected.
Medical management involves using medication called trilostane, which reversibly inhibits the production of steroids from the adrenal gland. This drug is the safest medical option, however is not without its risks. If the dose is too high for a particular patient, they can have a lack of steroids in their system, which is also an issue!
Most patients will need ongoing blood testing every 1-3 months to ensure their level of steroid in their system is within a normal range. The dose and the frequency of dosing can be adjusted according to the progression of disease.
Prognosis for patients suffering from hyperadrenocortism will depend on the severity of the clinical signs, the treatment choice, any other diseases present and the commitment of the owner in the case of medical management.
Should you think your pooch may be a potential candidate for Cushings disease please book in an appointment for a check up. For more information please give one of our friendly team a call.