To function properly and harmoniously, the body needs to manufacture hormones through its endocrine system. Hormones are small chemical molecules produced by one organ and acting on another organ. They have a role of messenger and regulator of metabolism. Hypercorticism in dogs is a common problem.
Skin of dog with hypercorticism: this photo shows comedones, telangiectasia and calcinosis lesions.
Among these hormones, there is “cortisone” or more precisely cortisol. It is a hormone of the steroid family (glucocorticosteroids). This hormone consists of cholesterol from two glands a few millimeters above kidneys: the adrenals. It is the external region of these glands, the cortex, which manufacture them: we speak of adrenal cortical glands.
The regulation of cortisol secretion by the adrenal glands is controlled by two other glands located in the brain. These glands are hypothalamus and the anterior pituitary. The hypothalamus releases a first hormone, CRH (Corticotropin-Releasing Hormone). It acts on the anterior pituitary to stimulate the production of pro-opiomelanocortin (POMC). And, it will become, after various stages of maturation, ACTH (adrenocorticotropin). It is ACTH, produced by the anterior pituitary. It acts on the adrenal cortex glands to stimulate the release of cortisol.
The hypothalamus-antehypophysis-adrenal cortex axis is called the “corticotropic axis”.
The cortisol thus produced acts on many levels. The carbohydrate and protein metabolism, the skin, the kidneys, the bones and ligaments, the blood, the sexual glands, etc.
In dogs, there may be a disruption of this corticotropic axis, called “hypercorticism”. It causes excessive production of cortisol in the body. We also speak of Cushing’s disease or Cushing’s syndrome. When the initial disturbance affects the anterior pituitary or the adrenal cortex, respectively.
Causes of hypercorticism in dogs
There are classically two types of hypercorticism (HC). One is a pituitary form (HCH) in 80% of cases and other is an adrenal form in 20% of cases (HCS).
Pituitary hypercorticism is most often found in small dogs (<15kg) (75% of cases): it is linked to the presence of a small pituitary tumor (microadenoma) in 80% of cases, or to a larger tumor (> 10mm or macroadenoma) in 20% of cases (exceptionally non-tumor pituitary hyperplasia).
Adrenal hypercorticism find more frequently in large dogs (> 20kg). It is secondary to an adenoma (benign tumor). It is in 40% of cases or an adenocarcinoma (malignant tumor) in 60% of cases. The tumor affects only one adrenal cortex gland.
Typically, affected dogs are around 10 years old.
There is an “iatrogenic” hypercorticism which links to a chronic external administration of “cortisone”. This situation typically encounters. When a dog will treat for example for dermatological problems (itching, allergies, etc.) or an autoimmune disease. These diseases are anemia, polyarthritis, meningitis, etc. It is due to the repeated administration of “cortisone”.
- Polyuro-polydipsia (volume of urination and increased drinking)
- Polyphagia (increased appetite)
- Distension of the abdominal strap (dilated belly)
- Skin symptoms: alopecia (loss of hair) of the trunk, symmetrical and not itchy, thin and less elastic skin, comedones (“blackheads”).
- Skin symptoms:
- telangiectasia (dilation of small skin vessels), delayed hair growth, calcinosis (appearance of small calcified masses in the tissues). Other symptoms are dry seborrhea, skin superinfection.
- Urinary disorders: repeated urinary tract infections, urinary stones
- Neuromuscular symptoms:
- muscle weakness and atrophy, intolerance to exertion, ligament laxity (cruciate ligament rupture), pseudomyotonia of the hind limbs (stiffness), nervous disorders
- Respiratory symptoms: shortness of breath, snoring, sudden distress (pulmonary thromboembolism)
- Reproductive disorders: absence of heat in the female, feminization in the male
The diagnostic process to move towards hypercorticism carries out in three stages.
- Look for changes in the blood and urine frequently encountered in this disease. A biochemical and hematological blood test and a urine sample are necessary.
- Confirm or rule out hypercorticism. When there is a weak clinical suspicion, the veterinarian can carry out. It carries out from the morning urine collected by you, a urinary cortisol / creatinine ratio (RCCU). This test, if it turns out to be negative, makes it possible to exclude an HC with almost certainty. If it is positive, no conclusion is possible. When there is a stronger clinical suspicion, the veterinarian can perform two types of blood tests which are hormonal stimuli. It is stimulation with ACTH or weak braking with dexamethasone. Sometimes these tests must repeat to confirm an HC.
- Locate the site of hypercorticism. In order to know where the disorder is located (antehypophysis or adrenal gland), several diagnostic means are possible. Imaging exams are abdominal ultrasound and / or scan of the brain and abdomen. The blood tests includes strong braking of dexamethasone or dosage of endogenous ACTH.
When an adrenal tumor will detect, it is advisable to check for the presence of locoregional. Also, check distant metastases by imaging examinations (CT scan> ultrasound).
Treatment of hypercorticism in dogs
During pituitary hypercorticism, although surgical interventions –hypophysectomies – exist (many complications), the possible treatments are radiotherapy and medical treatment.
In adrenal hypercorticism, the treatment of choice remains surgery when the tumor has not metastasized and local growth remains moderate. In this case, medical treatment should put in place to stabilize the animal before the operation. This medical treatment is also possible in all cases of unoperated or unoperable adrenal hypercorticism.
Depending on the general condition of the animal, there are certain factors. These factors are medical and financial context, the efficacy and side effects of the drugs and the monitoring protocol. The veterinarian can adapt the treatment accordingly.
With the exception of a surgical intervention (possibly radiotherapy) which makes it possible to “cure” the animal. The medical treatment makes it possible to obtain a resolution of the symptoms. And to obtain a good quality of life of the patient animal. But in no case a disappearance of the tumor.
Monitoring and prognosis
Whatever the therapeutic decision, close monitoring of the animal is essential. The monitoring include both clinically and biologically (regular blood tests and urinary examinations). In order, in particular, to adapt the dosage of drugs.
Medical treatment, once in place, is necessary for life.
Any side effect (depression, anorexia, vomiting , diarrhea, tremors, etc.) requires treatment to stop and a check-up with the veterinarian.