Let us know what the specialist has to say. I too am waiting for my puppy gal to come into her first heat. She is 9 months old - but is a large breed dog not a puppy.
And she is a great age to do all the health testing necessary prior to breeding her, but for sure whether you breed her or not, I'd get a full blood panel done, and also the BAT specific blood test for liver function.
If the T4 on the full blood panel is low normal especially just over the borderline, I would do the expanded T4 panel, as the regular T4 testing will not always show up thyroid problems.
www.hemopet.org is an excellent source of information on thyroid and does due the testing. Dr Jean Dodd does respond to email inquiries too.