Addison's disease, also known as primary adrenal insufficiency, is a rare but serious condition that affects the body's ability to produce necessary hormones. There are several synonymous terms that may be used to describe Addison's disease, such as adrenal insufficiency, hypoadrenalism, and hypocortisolism. Symptoms of the condition can include fatigue, weight loss, low blood pressure, and darkening of the skin. Treatment typically involves hormone replacement therapy to address the hormonal imbalances caused by the disease. It is important for individuals with Addison's disease to work closely with their healthcare provider to manage their condition effectively.