I had a hysterectomy about 3 months ago, and afterwards my hair starting falling out at an alarming rate. I was quickly getting bald spots on the top. At about the two month mark, new hair started growing in. Here are the things I did: Took 2 tablets a day of biotin, increased my protein intake, got acupuncture with needles in the head to stimulate circulation (not as bad as it sounds), and used Murad professional scalp treatment for thinning hair (leave it in for about 5 minutes or until your scalp tingles).
Also, I had been taking a lot of progesterone before the surgery and that had changed the texture of my hair to very fine and fly-away. Now I no longer need the progesterone, and my hair is a much better texture. I think it took a few months to get the progesterone out of my system.