My Yorkie was diagnoised with cushings disease, 4 years ago My Yorkie tilly had started drinking way to much water like she couldn't get enough which gave me a red flag that's not normal..So I took her to her vet and explained her(excessive water drinking). He ran test and she has cushings I am not saying your yorkie has it, but it does go unnoticed It is treatable, please check at the address below for complete symptons. This disease affects yorkies & other small breeds. Good luck
http://www.marvistavet.com/html/cushing_symptoms.html 