Addison's disease, or hypoadrenocorticism, occurs when a dog's adrenal glands do not produce enough hormones, primarily cortisol and aldosterone. This condition can lead to a variety of symptoms, including lethargy, vomiting, diarrhea, and a lack of appetite. In more severe cases, it can cause a life-threatening crisis known as an Addisonian crisis, where the dog may experience shock due to dangerously low levels of these hormones. Diagnosis typically involves blood tests and possibly imaging studies, while treatment usually consists of hormone replacement therapy to manage the condition. Understanding Addison's disease is important for dog owners, especially as they consider the long-term health and longevity of their pets. The adrenal hormones that are deficient in this disease play critical roles in regulating metabolism, immune function, and overall energy levels. Addressing Addison's disease early through proper veterinary care can significantly improve a dog's quality of life, thereby potentially enhancing their lifespan. Additionally, as geroscience continues to explore longevity, managing chronic conditions like Addison's may play a role in how well dogs age, as stable health is a key component in promoting longevity.