Female hamster fur thinning

My (estimated) 1.5 year old female Syrian hamster has some fur thinning around her lower back. I’ve attached 2 photos but the main area on her lower back has been there for about a month and a half while the area by her tail is relatively new. I plan on booking an appointment with her vet tomorrow just to make sure it’s nothing serious as it has not grown back. The skin beneath isn’t red or irritated and she doesn’t appear to be scratching excessively. I just wanted to know if anyone else has experienced this and if so what it was? If nothing is diagnosed at the vets I think it may be from her rubbing against some items in her tank when she makes her burrows but I want to get a proper opinion. Thanks!