White Hair on a Previously Black Dog

[btr323]

So today I noticed a patch of silver/white hairs growing on the underside of Gypsy's tail. Her tail, like most of her body, is solid black. (I'd attach a picture if I could figure out how to do it on here.) For whatever it's worth, Gypsy does have some white patches--namely, on her chest, under her muzzle, and on her feet--but those patches have remained static. And she's only six months old, so (I'd imagine) she's way too young to be graying.

Call this an overabundance of caution, like when I took Gypsy to the vet the day of her first tick bite. But I've been doing some reading online that suggests premature graying can be a sign of thyroid or liver issues. (In addition to the "conventional wisdom" I've heard that it's a sign of severe stress.)

Is this something any of y'all have encountered? Should I be scheduling a vet appointment about this? Or am I just being an over-protective puppy owner?

[delladooo]

To put photos on they have to be hosted on an external site (eg photobucket / flickr etc.) and then include it in IMG brackets.

My all black dog occasionally gets a few white hairs, personally I wouldn't worry unless a very large patch occurred and didn't disappear. That said, I wouldn't necessarily worry with a puppy as much anyway - a friend's staffy cross was all white but now at 6/7 has loads of black spots so I don't think it's necessarily a problem