Three broad categories of hypercorticism (excess glucocorticoid/cortisone in the blood) can be established based on their origin
- pituitary (the pituitary gland is a small gland located under the brain) (PDH: Pituitary Dependant Hyperadrenocorticism)
- adrenal (the adrenals are glands located near the kidneys) (AT: Adrenal Tumour)
- iatrogenic (induced by the administration of cortisone-containing treatments)
- Breed: Any breed of dog can develop hypercorticism but Poodles, Dachshunds and Terriers (especially small ones: Yorkshire, Boston, Jack Russel) seem to be more often affected.
- There is no breed, age or sex that predisposes to the development of iatrogenic Cushing's.
- Polyphagia (increased food intake), Polydypsia (increased drinking) and Polyuria (increased urination)
Daily water consumption of more than 100 ml/kg of body weight is seen in 32-82% of affected dogs. These clinical signs may precede skin changes by 6-12 months.
Polyphagia is found in more than 50% of cases: owners often consider this symptom to be a sign of good health!
- Abdominal distension: "pendulous abdomen
Redistribution of fat in the abdomen, hepatomegaly (large liver), bladder distension and weakness of the abdominal muscles are the cause.
- Neuromuscular / neurological signs
- Sexual signs :
Anoestrus (the bitch does not come back in heat) / testicular atrophy
- Respiratory signs
Gasping and increased respiratory rate are the most common signs. Pulmonary thromboembolism is sometimes seen.
- Dermatological signs
First of all, the coat loses its shiny, silky appearance and becomes more difficult to comb.
Over time, the hair begins to disappear, causing a decrease in its density (hypotrichosis); this is followed by alopecia (absence of hair). It is in most cases symmetrical, invading the trunk, but spares the extremities of the limbs and the head. A change in coat colour is often an early sign.
The skin becomes hypotonic, thin, often revealing the underlying vascularity. Numerous comedones may be observed. Changes in the skin vessels (phlebectasia, petechiae, etc.). Poor wound healing and cutaneous calcinosis may be part of the clinical picture.
- Biological tests (fasting blood test)
- Haematology and blood biochemistry are disturbed
- Thyroid hormones are decreased in 34-55% of cases of hypercorticism
- Biological tests (urine collection: the dog must not have urinated before the consultation as urine is ideally collected by bladder puncture)
- A urinary infection is present in +/- 50% of cases
- Specific tests are necessary to establish a precise diagnosis: ACTH stimulation, endogenous ACTH dosage, dexamethsone braking, urinary cortisol/creatinine ratio...
- X-rays can also be used to demonstrate mineralisation of the adrenal glands
- Ultrasound is the method of choice for visualising the adrenals, but it requires quality equipment and an experienced operator.
- Nuclear magnetic resonance allows the pituitary gland to be visualised with precision.
- This serious disease is treated medically with either Mitotane or Trilostane.
- Surgery can also cure some cases. It consists of removing the adrenal tumour in the case of an adrenal tumour (difficult surgery because the tumour often invades the vena cava) or by transphenoidal hypophysectomy in the case of a pituitary tumour (this technique is only carried out in certain specialised centres and presents significant risks).