Addison's disease, also known as primary adrenal insufficiency, results from the insufficient production of cortisol and sometimes aldosterone by the adrenal glands. Due to the lack of cortisol, patients exhibit symptoms such as profound fatigue (weakness), muscle pain, and low resistance to stress (due to cortisol’s role in the stress response). Contrary to options A and D, Addison’s disease typically causes **hypoglycemia** and **low blood pressure (hypotension)**, not hyperglycemia or hypertension.