After a career as a sports shooter Thor-Øistein Endsjø became a leading sports doctor in Norway. Endsjø was a skilled pistol shooter and won five Norwegian titles. This earned him a place on the Olympic team for the 1972 München Games where he came 17th in the 25 metres event. Following his sports career he worked as a physician in clinics in Norway including one he co-founded in the city of Sandvika. Endsjø then became the team doctor for Norway at five editions of the Olympics, with him also working with the Norwegian Athletics Association.