So does it grow back eventually?
Yes it will! In fact, my friend (RNY) said that her hair grew back in healthier than ever. She had thyroid issues and other problems that dried her hair out. She lost her hair fairly quickly. It didn't all come out at once, but it became thinner. She moved away before I could see her hit her goal weight. She said once she started to maintain, her hair came back shiny and healthy.
The type of hair loss we get is telogen effluvium which means there is either a shock to our system or something lacking in our bodies that causes a lot of our hair to go into the resting phase at once so they fall out. If whatever the trigger is eliminated, your hair will grow back just fine. So let's say your hair is falling out because of anesthesia. In about 3 months the first few hairs that fell out will start growing back. If they're falling out due to an iron deficiency or malnourishment (sp) and you haven't fixed the problem then the hairs that fell out 3 months ago will start to grow back but you will continue to lose hair and have chronic telogen effluvium until the problem is fixed. There are types of hair loss that don't grow back but those have to do with hormones, auto immune disorders and physically damaging your hair follicles.