By Michelle H. Patrick, VMD, MS, DACVIM (SAIM)
Discover the complexities of Addison's disease in dogs, including diagnosis, treatment options, and management strategies for hypoadrenocorticism.
Hypoadrenocorticism, also known as Addison’s Disease, is an uncommon condition, with an estimated prevalence between 0.06% and 0.28%. Known as “the great pretender,” its vague, nonspecific clinical signs often mimic other illnesses, as do diagnostic findings. Early recognition, diagnosis, and treatment can prevent significant mortality secondary to hyperkalemia, hyponatremia, dehydration, and hypovolemic shock.
The adrenal gland comprises an inner medulla and an outer cortex. Three layers make up the cortex, and each is responsible for hormone production. The outermost layer, the zona glomerulosa, is responsible for mineralocorticoid (aldosterone) production, while glucocorticoids and androgens are produced by the zona fasiculata (middle layer) and reticularis (innermost layer).
Primary hypoadrenocorticism is most common and is most often caused by autoimmune destruction of the medullary layers. Thus, destruction of the zona glomerulosa results in mineralocorticoid deficiency, while cortisol (glucocorticoid) deficiency occurs secondary to destruction of the zona fasiculata and reticularis.
Secondary hypoadrenocorticism is rare. It is caused by lack of secretion of adrenocorticotropic hormone (ACTH) from the pituitary gland or lack of secretion of corticotropin-releasing hormone (CRH) from the hypothalamus. This, in turn, results in atrophy of the zona fasiculata and reticularis, and therefore lack of cortisol production; mineralocorticoid production from the zona glomerulosa is not affected. Secondary hypoadrenocorticism most commonly occurs secondary to neoplasia or intracranial trauma.
Most dogs with primary hypoadrenocorticism are deficient in both glucocorticoids and mineralocorticoids; however, glucocorticoid deficiency can occur without mineralocorticoid deficiency. The latter population lacks electrolyte abnormalities; this is referred to as ‘atypical.’ These dogs can progress to develop mineralocorticoid deficiency, so sodium and potassium should still be monitored in these patients.
This article originally appeared on dvm360.com on November 19, 2025, as part of Thrive Pet Healthcare's Strategic Alliance with dvm360.
About Michelle H. Patrick, VMD, MS, DACVIM (SAIM)
Dr. Michelle Patrick, originally from Coal Township, Pennsylvania, is an internal medicine specialist at Thrive Pet Healthcare Specialists in Miami, Florida. She earned her bachelor’s degree in biology from Susquehanna University and her Doctor of Veterinary Medicine from the University of Pennsylvania School of Veterinary Medicine. She completed an internship at a private practice in South Florida, followed by a residency in internal medicine at Washington State University’s College of Veterinary Medicine, where she also earned a master’s degree in veterinary medicine.
Dr. Patrick has been practicing internal medicine in Florida since 2010, previously working at Southwest Florida Veterinary Specialists and VCA Palm Beach Veterinary Specialists. Her professional interests include immune-mediated diseases, gastrointestinal disorders, and endoscopy.
