Yin/yang, zig/zag, dogs/cats: For every action, there is a reaction. In veterinary medicine, when something goes up, something can go down. Last month, we discussed hyper (high) adrenocorticism (Cushing’s disease); this month is about hypo (low) adrenocorticism, or Addison’s disease.
Just as in Cushing’s, Addison’s can manifest itsself as primary and secondary hypoadrenocorticism. It also can be acute or chronic. Acute forms are bad news because so much goes wrong so quickly that your diagnostic tool belt may not give you a speedy answer.
Addison’s creates a syndrome that results from the insufficiency of two corticosteroids: glucocorticoids and mineralocorticoids. The lack of these steroids in the body can show up as other diseases, making definitive diagnosis hard work. Of all the diseases that mimic other organ system failures, Addison’s is the topper of all, taught in school as the ‘Great Pretender.’
Primary Addison’s is caused by damage to the outer layers of the adrenal gland, the cortex—the area that produces these corticosteroids. The adrenal gland responds to the pituitary gland’s requests also, and if the pituitary gland stops requesting action, the adrenal gland will just sit there twiddling its thumbs, resulting in loss of glucocorticoid production, while the mineralocotricoid portions stay the same. When that occurs, you have secondary Addison’s disease. Damage to the adrenal gland and pituitary gland can result from tumors in these glands, as well as a number of other causes, even responses to certain medications. Either way, your dog or cat is Addisonian.
Addisonian animals are usually seven years and younger. Cats have no breed or sex predilection, but dogs of the fairer sex are at a higher risk. Depression, lethargy and weakness are the top three symptoms. Your pet could have intermittent bouts of vomiting and/or diarrhea, with some lack of appetite.
Acute Addison’s disease can be a little more helpful to the diagnostician, but that’s because the symptoms can be so dramatic. Easier for the doctor, maybe, but much harsher on the pet, as acute patients can suddenly collapse from weakness, a slowing heart, and bad heart rhythms. This sometimes leads to shock! Who feels like eating when you feeling horrible, vomiting, and down in the dumps? With Addison’s, your pet is far more ill than you can realize when you come home from work and you see your best friend depressed and reluctant to move. That is when you get a blood sample.
My last case of Addison’s disease started off looking like a Cushing’s dog with severe kidney failure, that is until the potassium finally spiked. Thank St. Francis, ‘Belle’s’ owner continued to allow for further testing to track all the other abnormalities. This allowed me to witness high potassium and low sodium levels, which lagged the illness by several days. Addison’s is low steroids, but hallmarked by high potassium. In Belle’s case, the early blood tests were too early to detect the electrolyte changes. When your electrolytes are in a tizzy, all manners of bad things happen, even metabolic acidosis, where the pH of your pet’s blood becomes acidic. Secondary Addison’s almost always shows normal potassium and sodium levels, making it extremely tough to diagnose.
So we test some more. Oddly, the best test is the exact same one as one of the tests for Cushing’s disease. The next test is called the ACTH stimulation test, where a synthetic hormone is injected, prompting a ramp up in corticosteroid production. If that prompt results in a big ole goose egg, you’ve got Addison’s. You also can test the amount of natural ACTH in your pet’s serum. Primary Addison’s, and you’ll have way too much, because the pituitary is screaming, Do your job, you lazy adrenal gland! not knowing the adrenal is hurting. In secondary Addison’s, the ACTH level is sometimes undetectable, because the pituitary is hurting and can’t make any more ACTH, and the adrenal gland has nobody telling it what do, which means, no corticosteroid production.
To treat, you must clean up the mess. Fixing electrolyte levels is top priority and you can see the patient improve before your eyes. Then we have to replace what’s missing: our mineralocorticoids AND glucocorticoids in primary Addison’s and just glucocorticoid supplementation in secondary Addison’s.
There is the Addison Yang to the Cushing’s Yin. It always amazes me how hormones and steroids rule our roosts and how a glitch here or there can cause an avalanche of illness. Do not fear, your vet will be there to help.