4 yr old boxer hair loss

Question
My 4 yr old female Boxer has never had any allergy or health issues before but is now starting to loose her hair around her hips and there is a dark circular spot in the middle on one side. She doesn't itch, it's not red or irritated, and it doesn't seem to bother her at all. Some of the hair is starting to grow back on the patch with the spot in it but now the opposite hip is just starting to loose hair. I don't think it's do to food, environment, or anything like that because nothing has changed in about 2 years. It started about the beginning of January. We don't have much $ to go to a vet (we will be tho) so I'm hoping to narrow down what he can test her for so the cost isn't too expensive if possible.

From everything I've read about skin conditions in dogs it sounds to me like it could 1 of 3 things:

1) Seasonal Flank Alopecia
2) Hypothyroidism
3) Cushing's Disease

I don't know much of anything about dogs skin conditions tho so I was hoping for a 2nd opinion, please?

Answer
The vet really needs to evaluate it first before deciding on testing, but it could possibly be ringworm, a fungal disease, which would be treated with a medicated shampoo. It does seem odd to me though that she is loosing hair in exactly the same spot, but on the opposite side... but that could just be coincidental.

When one of our dogs had ringworm, she had small circular spots along her topline. The vet used a blacklight on her spots (but only two varieties of ringworm are detected that way), and the crud from the spots was cultured. It was cleared up with medicated shampoo.

http://www.dogchatforum.com/ringworm-in-dogs.htm