Conditions or characteristics that can be both an exposure and an outcome

I have spoken about “exposures” and “outcomes”. These are very important concepts in
epidemiology. You will be thinking about these throughout the entire course and beyond.
Sometimes things are not as clear-cut as we would like them to be. There are quite a few
conditions or characteristics that can be both an exposure and an outcome!
Please provide an example of one of these conditions and explain how it could function as an
exposure and how it could function as an outcome.