After some thought I’ve decided to write this article in plain English for the benefit of the average dog owner. If you wish to see a more thorough explanation or bibliography, click here.
As you may know, cortisol is our natural anti-inflammatory hormone. It plays a role in essentially all body functions and is necessary for the body’s survival.
Cortisol is created when the brain sends out a fancy chemical call adrenocorticotropic hormone (ACTH) into the bloodstream. ACTH stimulates the adrenal gland to convert precursor hormones (building blocks) into cortisol. It’s like an assembly line. One hormone molecule Is converted into another until it’s turned into cortisol.
When the brain senses that sufficient cortisol has been produced, it decreases ACTH production, thereby decreasing adrenal gland activity. This feedback loop is a little like the thermostat in your home. When the house is warm enough, the thermostat turns off the furnace.
Adrenal exhaustion is a condition where the body can NO LONGER CONVERT the precursor hormones into cortisol. This may be due to chronic stress, chemical damage, and/or genetic abnormality. Over the years, the veterinary community has called this condition by various names: hyperestrogenism, atypical Cushing’s disease, and Plechner’s syndrome.
When the glands can no longer convert precursors into cortisol, it creates a break or interruption in the assembly line. The precursor hormones pile up behind that break. With nowhere else to go, they are rerouted down an alternate assembly line to produce hormones called adrenal sex-hormones.
Furthermore, because the glands are no longer producing sufficient cortisol, the brain never receives the message to turn off ACTH production. This causes chronically elevated sex-hormone levels. Since the sex-hormones are steroids, the resulting symptoms look almost exactly like those of cortisol excess (Cushing’s disease). This is why a dog in adrenal exhaustion can mistakenly appear to be suffering from Cushing’s disease.
Low dose cortisol supplementation can reestablish the feedback loop. The brain recognizes the presence of the cortisol replacement and reduces ACTH production. Once the ACTH production is normalized, levels of sex-hormones begin to normalize as well. This is how low-dose cortisol replacement therapy reduces elevated sex hormone levels and the symptoms so common in SARD dogs.
Because low dose cortisol replacement simply replaces what the body would normally make, we do not expect to see the side-effects produced by high, anti-inflammatory doses of prednisone or other glucocorticoids.
On the other hand, if aggressive treatments for Cushing’s disease are implemented — treatments that destroy what little cortisol production exists — there can be life-threatening results. When dealing with a SARD dog, test sex-hormone levels, especially estrogen.
I hope this helps you and your dog.