Hi, I am a registered nurse and also have experienced this exact thing. I was losing my hair as well. I tried everything… nobody could tell me what was wrong. The only thing that changed it was when I randomly started taking a zinc supplement. No more hair loss, and my brows have grown back. Also, losing certain parts of your brows can be indicative of a thyroid issue, or possibly hormonal. Demand your doctor checks everything girlfriend… you have to advocate for yourself. If you wait around for someone else to fix it, you will never get to the bottom of it.