Addison’s disease, also known as hypoadrenocorticism, occurs when the adrenal glands stop functioning. This condition is typically caused by immune-mediated destruction of the adrenal glands, a process where the body attacks its own tissue. The adrenal glands are small glands located near the kidneys that secrete two important substances, cortisol and mineralocorticoids. Cortisol is responsible for digestive health and regulation of white blood cells and glucose. A lack of cortisol can lead to intestinal symptoms such as vomiting, diarrhea, and not eating. It can also lead to low blood sugar. Mineralocorticoids are responsible for water balance as well as balance of electrolytes such as sodium and potassium. Lack of mineralocorticoids can lead to severe dehydration, increased kidney values and weakness, collapse, and even death.
If we suspect that a patient has Addison’s disease, we perform a blood test called an ACTH stimulation test. The first blood sample we obtain will determine the patient’s baseline (starting) cortisol level. Next, we give an injection of ACTH which stimulates the adrenal glands to produce cortisol. One hour after the injection, we draw another blood sample. Since the adrenal glands don’t produce cortisol in a dog with Addison’s disease, we will see little to no change in the cortisol levels before and after stimulation with ACTH.
While often very sick when diagnosed, patients with Addison’s disease can live long and healthy lives. Since the adrenal glands are completely destroyed with this disease, patients will never again produce these important hormones. Therefore, they will need to be supplemented with these hormones for the remainder of their lives.
Prednisone is the replacement for cortisol. If a patient is very ill at the time of diagnosis, we will give a higher than physiologic dose (doses made by the adrenal gland under normal conditions) of prednisone for a few days. Common side effects patients may experience at this dose are drinking and urinating more and an increased appetite. Once the body has fully recovered, we then decrease the dose to what is considered a physiologic dose and eliminate the side effects associated with the higher initial dose. Our goal is to supplement only what the body needs; therefore, doses will vary for each patient.
Percorten injections are the mineralocorticoid supplement. This injection is given once every 21-30 days. The frequency of administration will vary for each patient. We typically recheck electrolytes 21 days after the injection. If the potassium is high and the sodium is low, it is time for another injection. If they remain normal, we recheck them every 3-5 days until a change is identified. That then tells us how frequently the patient requires injections and these injections can eventually be given at home at that interval.