Well....I'm not on HRT, and I've noticed the hair thinning for the last three years. I don't think it's anything to do with HRT, it's just simply part of being a woman, hormones and meno. Last year, I lost all the top layer of hair due to sudden breakage or loss ....I looked like suzi Quattro with a feather cut for ages. I used to have long thick hair and it may be vain- but it's one of the worst of the many symptoms of menopause for me. I have been taking Incite Biotin and MSM (Amazon) and using Kerastase Oil ultime and it's helping.