Dog has hair loss on tail...Conditions that might cause?

I know a vet needs to see this dog and bloodwork done to be certain. However, I know there are some conditions that could cause this and would like to get some thoughts ahead of time. The dog is a long haired dauchund female(not spayed) that is around 5 years old. She recently started losing hair along her tail, just along the the tail bone. It looks like a rat tail and I know I've heard of some diseases that this can be a symptom of. Hypothyroidism and Cushing's disease are sticking out in my mind and I like your thoughts.

Please don't mention fleas because I assure you she has none and the hair loss isn't anywhere else. She's isn't itchy either, the hair is just thinning almost completely gone along the vertabrae of her tail.

Dog has hair loss on tail...Conditions that might cause?

Hypothyroidism and Cushings popped into my mind immediately.

I'd take her to the vet for some bloodwork to be sure.

Dog has hair loss on tail...Conditions that might cause?

Cushings is a very good possibility as is hypothyroidism which you mentioned. Those would be a great place to start.

Dog has hair loss on tail...Conditions that might cause?

DOES SHE WAG HER TAIL ALOT AND HIT IT AGAINST HARD PLACES? JUST A SUGGESTION I KNOW MY PIT BULL DOES THAT AND AT TIMES IT GETS SO BAD TO THE POINT THAT IT STARTS TO BLEED. WHATEVER THE CAUSE GOOD LUCK.

Dog has hair loss on tail...Conditions that might cause?

thyroid problems will do this.

Dog has hair loss on tail...Conditions that might cause?

it could be stress or nerves. i had a dog do that and the vet gave him one pill and it went away for good, the hair grew back in less than a week. the pill was only like $6.