Theodor Kocher was a very important doctor who lived a long time ago. He worked in Switzerland in the 1800s and did really amazing things to help people who were sick.
One of the things that made him really special was that he became famous for doing surgeries on people's thyroid glands. The thyroid gland is a little piece of your neck that helps your body work the right way. If something goes wrong with it, you can get very sick and it can be hard to fix. But Theodor Kocher figured out how to do surgery on the thyroid gland to make people feel better.
He did this surgery a lot of times and he wrote down everything he did so that other doctors could learn from him. He even won a really big prize for being so good at doing surgeries on the thyroid gland.
Theodor Kocher was also a really kind person who liked to help other people. He taught lots of other doctors how to do surgery and he was always trying to find new ways to help people who were sick. Even though he lived a long time ago and passed away over 100 years ago, he is still very important and people remember him for being such a great doctor.