I'm puzzled by the history you've provided. Chronic bleeding from both the gastrointestinal tract and urinary tract suggests a bleeding disorder such as immune mediated hemolytic anemia or, less commonly, a coagulation defect such as hemophilia. Chronic bleeding will cause hypoproteinemia (decreased blood proteins). Can you tell me, please, if testing directed toward these types of bleeding disorders has been performed - a careful exam of the red blood cells for the presence of spherocytes (a shape suggestive of autoimmune hemolytic anemia), testing for autoagglutination (pathognomonic - particularly indicative of - for autoimmune disorders), ANA and LE prep testing? Has the anemia been classified as non-regenerative (your dog can't replace the red blood cells he's lacking) or regenerative (your dog is replacing the red blood cells he's lacking). This is done by checking his reticulocyte count.
I'm also puzzled by "thyroid problems" at 3 years of age. Thyroid levels can be depressed secondary to systemic disease. The thyroid gland may actually be healthy. Until his bleeding disorder can be clarified, I wouldn't put much stock in a low T4 at this time.
I need to know quite a bit more to be more accurate for you. I'd be pleased to review any testing that's already been performed. You can upload test results to our conversation. If you need help doing so, please contact [email protected]
Please respond with additional information and further questions or concerns if you wish.