Last week was a big week for adrenal gland disorders at The Animal Medical Center. Not one, but three dogs were admitted by The Animal Medical Center’s 24-hour Emergency Service with a diagnosis of Addison’s disease, or hypoactivity of the adrenal gland. Additionally, I evaluated two of my patients for adrenal gland hyperactivity, or Cushing’s disease.
Small but Mighty
Adrenal glands are tiny organs, one sits atop of each kidney. The normal width of a dog’s adrenal gland is less than half an inch. In cats, adrenal glands are half that size. Small compared to the liver or kidneys, these glands are powerhouses pumping out an array of hormones critical to maintaining normal homeostasis. Because the adrenal glands produce so many different hormones, either condition hypo- or hyperactivity can cause a wide variety of serious clinical signs. The hormone most important in Cushing’s and Addison’s disease is cortisol.
Two of last week’s ER patients with Addison’s disease were poodles. This was no coincidence. Addison’s disease is inherited in the Standard Poodle and also the Portuguese Water Dog, Nova Scotia Duck Tolling Retriever and the Bearded Collie. Cats very rarely develop Addison’s disease. What is strange about the dogs at AMC is the diagnosis of Addison’s disease in three dogs in one week, since the prevalence of the disease in dogs is thought to be 0.6-0.28% of all dogs. Dogs with Addison’s disease have vague, nonspecific clinical signs such as vomiting and diarrhea. One reason your veterinarian performs blood tests when your dog has vomiting and diarrhea is to identify the characteristically low blood concentrations of sodium and chloride and the high concentration of potassium, classic for a diagnosis of Addison’s disease. The consequences of missing a diagnosis of Addison’s disease are dire. Dogs become progressively dehydrated and the potassium climbs to levels which can stop the heart from beating. The AMC ER has a machine which can test blood concentrations of sodium and potassium in minutes, speeding the diagnosis of Addison’s disease.
Too Much Water; Too Much Pressure
The adrenal glands of dogs with Cushing’s disease produce too much of the hormone cortisol, either because of an adrenal tumor or because the pituitary gland in the brain forgets to tell the adrenal glands to stop producing cortisol. The two patients I evaluated for Cushing’s disease had different medical problems. One dog had an increased amount of protein in her urine, high blood pressure, and an elevated liver test. All three disorders are known to occur as a result of Cushing’s disease. The other dog was drinking too much water and having accidents in the house — two more signs of Cushing’s disease. Neither dog had hair loss, but it is another common problem we see in dogs with an overactive adrenal gland. Cushing’s disease, like Addison’s disease, is rare in cats.
Giving and Taking Away
Treatment for these two opposite diseases is opposite! For Addison’s disease we give hormones, and for Cushing’s disease we take the hormones away by suppressing the adrenal glands. Dogs with Addison’s disease respond rapidly to either oral or injectable forms of the missing adrenal hormones. Treatment of dogs with Cushing’s disease takes a month or two, while oral medications are adjusted to individualize the dose for each dog.
Recognizing the Yin and Yang of Adrenal Gland Disease in Your Dog
Even though Cushing’s disease is more commonly seen than Addison’s disease, both diseases can be readily diagnosed with blood tests. Your veterinarian will suggest testing if your dog is showing the following signs:
- Excessive drinking and urinating
- Hair loss on the trunk
- Elevated liver tests
- High blood pressure
- Protein in the urine
- Pot-bellied appearance
- Waxing/waning vomiting and diarrhea
- Poor appetite
- Weight loss
- High blood potassium
- Low blood sodium and chloride