I took a steroid and my hair is falling out. I stopped it in about a month, but it is still falling out. I have been on Propecia for a few years so I thought that would protect me. What will happen to me? Have I messed up my hair?

You probably precipitated what we call a telogen effluvium, which can be caused by steroid use. Once this begins there is nothing that will reverse it until it goes its course. I always tell my patients that although Propecia may protect you somewhat, it is not a sure thing when you take steroids. I would strongly suggest that you continue with the Propecia. As the hair loss may take months to go its course, stay on the Propecia and wait it out. See your hair doctor as well, so that good baselines can be taken to compare with what will evolve over time. By having measurements to compare, at least you will know when the process has stopped, when it reverses, and what to expect. Advise your friends not to do what you did, so that you can help someone else avoid the problem you had.