This directed case study follows the story of the diagnosis and treatment of “Jazmyne,” an elderly feline patient with hyperthyroidism. The case asks students to practice the skills of observation and inference while making a diagnosis based on Jazmyne’s clinical signs and patient history. Students consider how observed clinical signs may correspond to physiological abnormalities. Throughout the case, students explore thyroid function by considering thyroid hormones, feedback loops, diagnostic tests, and treatment options. Students are asked to justify their decisions and actions with respect to prognosis, outcome, cost, feasibility, and ethics. The impact of environmental factors on animal health and the concepts of correlation versus causation are explored as students practice reading and evaluating primary literature to improve patient outcomes. Designed to supplement a physiology unit within a college-level biology course, the case is best suited for students enrolled in a second-year biology, animal science, or physiology course.