Hair loss is common.
...After any surgery, especially one that dramatically changes your nutritional intake; it's called "telogen effluvium." it's temporary, and the hair will grow back, but it might take awhile (weeks to months).
It's worrisome, i know; happened to me after an operation, and i knew what it was, and knew it would grow back, and it still freaked me out! but rest assured, it's a temporary thing.