Hi hair thinining is one of the side effects listed for Tamoxifen. I've had problems with hair growth whilst being on it - I started Tam straight after chemo nearly a year ago and it's so thin I still have to wear a scarf:( I've read elsewhere that it should come back once you stop taking the tablets. With any of these treatments different people will have different reactions. Best have a chat with the helpline here or your oncologist if you are very worried.