2) Thyroid Problems
Although thyroid problems aren't common in this breed, it can certainly happen even in toy breeds and is something you should pay close attention to. This can cause your dog to suddenly drop weight fast. A thyroid condition would require medications prescribed by your pet's vet.
Diabetes in dogs is typically inherited from the parents, so before purchasing a dog or puppy, try to obtain medical records from the owners of the parents. If your dog has diabetes, he or she will need to be seen by a vet in order to come up with an effective treatment plan.