Cushing’s Disease or Hyperadrenocorticism

Overview:

Cushing’s Disease is a condition of excess cortisol (steroid) in the body. The adrenal glands located next to the kidneys are the organs responsible for steroid production. They are prompted to release cortisol into the bloodstream by the pituitary gland located at the base of the brain. Poodles, dachshunds, Boston terriers, boxers, and beagles are at an increased risk of developing Cushing’s. Dogs are more prone to have Cushing’s-the disease is rare in cats.

Causes:

The most common cause of excess cortisol secretion is due to a tumor of the pituitary gland. These tumors are usually benign, and make up 80% of Cushing’s Disease patients. The other 20% involve either an adrenal gland tumor (benign or malignant) or excessive steroid administration from the owner or veterinarian.

Symptoms:

Almost all patients with Cushing’s will drink, urinate, and eat excessively-these are the clinical signs that most owners notice first. The pet may also lose hair, pant excessively, become lethargic, and have a pendulous or bloated abdomen. Their skin bruises easily and can actually be thin and tear. Their liver will become quite enlarged and owners think the pet is gaining weight in the belly.

Treatment:

Unless the condition is due to a tumor of the adrenal gland, treatment is palliative, and not curative. Pituitary tumors are not removed, so clinical signs are simply managed. This disease can also be very hard to diagnose, as many of the tests available can have false negatives (the test shows patient does not have the disease when in fact they do). Sometimes, it is required to repeat the tests many times.Cats with Cushing’s tend to have a poor prognosis as most oral medications do not improve their signs. Their best treatment is usually surgery to remove one or both adrenal glands, but steroid replacement is required for the rest of their lives. It should also be noted that 80% of cats with Cushing’s also have diabetes.  Dogs have many more options than cats. Lysodren (mitotane) is still the drug of choice to treat Cushing’s. Owners need to be aware that their pet may appear sicker (vomiting, diarrhea, weakness) during the first week or two of therapy. This is not uncommon, but does warrant a phone call to the veterinarian immediately. This medication destroys part of the adrenal glands and there is a fine line between what is therapeutic and what is toxic. Once the patient is on maintenance dosing (usually 2 to 3 times weekly), they feel much better. Remember that all Cushing’s patients will require medication for the rest of their lives.Trilostane is an oral medication that is used in Europe and has just been approved to use in the United States. It appears to be as effective as Lysodren and may become just as popular for treatment.Ketoconazole and Anipryl are also used for Cushing’s, but are only indicated if the patient can not tolerate Lysodren or Trilostane.  They are not nearly as effective, although their side effects are mild.All pets with this disease will exhibit relapses and require medication adjustments. Routine blood tests are crucial to determine if the patient is receiving enough or too much medication. It is advisable to keep oral Prednisone handy just in case too much medication is given.  If the patient’s clinical signs are due to excessive steroid administration, discontinuing the medication should alleviate all signs.