Hair loss in a Z shaped pattern,4 yr.Yellow Lab

Question
Our 4 year old Yellow Lab has hair loss on both haunches in an odd "Z" type pattern and it appears dark in color or black and blue. It does not seem to bother her. When she was still young we took her to the vet for the same problem and the vet said it was hormonal and to have her fixed, We did and that seemed to help for a while but now it is back. What do you think? Thank you in advance for your time.

Answer
If you have taken this dog in to see this vet about this when she was younger and this has now returned, I would take her in again and ask him why. This is not something I can even make suggestions on over the internet. It has to be seen up close and hands on.

So call the vet and ask him what is going on now since she was spayed and it resolved and now it's back.

Only a vet in person can treat this.