My dog with Cushing's has low thyroid and is losing weight. Why?

Interpretation of thyroid test results should always be made with the whole picture in mind - this means taking into account whether Ollie has any symptoms of hypothyroidism, and also keeping in mind his other health issues which can sometimes affect thyroid results. Cushing's disease, along with other chronic health issues, can often cause artificially low results on a TT4 screening test, which is the thyroid test that most veterinarians do in-clinic. So for me personally, in this situation, I would make the decision about whether to recommend medication based on whether Ollie is showing any signs of a thyroid problem. Symptoms of hypothyroidism may include decreased appetite, weight gain, skin issues or poor haircoat, and decreased energy levels. If he's not showing any of these signs, it would be reasonable to decide not to start any treatment at this time. If you want to get a better idea of whether Ollie is truly hypothyroid, your vet can send a blood sample to a reference lab for a full thyroid panel - this can often help sort out whether there is an actual problem or not, in cases where it isn't clear.

As you know, Cushing's disease causes excessive cortisol (steroid) production, which can lead to an increased appetite. With the cortisol levels under control, Lucy's appetite may have regulated, but 13 pounds is a pretty significant weight loss. Normally, you should be able to easily feel (but not see) a dog's ribs and see a waistline when looking down on them from above. We can easily become accustomed to seeing overweight dogs as "normal" and can perceive a healthy weight as being too thin. (Without examining Lucy, I can't comment as to if she is truly underweight, or if her weight is appropriate.) Since her appetite has become picky and her Cushing's disease seems to be well controlled, there is also a chance that she has developed some primary intestinal issues (such as inflammatory bowel disease) chronic pancreatitis, or intestinal parasites. At this point, I recommend taking Lucy to her vet for another exam to assess her overall body condition and consider additional diagnostic testing (CBC, chemistry and abdominal ultrasound) to try to get to the bottom of this issue. I hope that all goes well!

If you have a copy of Milo's medical record, you can choose a Petco Pet Education Center, formerly Petcoach Consult to discuss this fully. Hypothyroidism does not usually cause weight loss in dogs, and the test may be caused by euthyroid sick syndrome, meaning the thyroid hormone is low because of some other illness. There are confirmatory tests that can help your vet decide if Milo needs to be on thyroid therapy. If there are no other abnormalities on a CBC and complete blood chemistry, then additional diagnostics may be indicated, including intestinal parasite screen, GI panel, x-rays, abdominal ultrasound, etc. If Milo has a good appetite without vomiting or diarrhea, you could try feeding more calories. I like Purina ProPlan Sport. You could also try puppy food, which is higher in fat. If you do decide to switch food, mix them together slowly over 2-3 weeks to avoid an upset stomach.

Poor Harley, that's quite a weight gain. If he does have Cushing's, it can usually be managed quite successfully with medication. Trilostane is the latest therapy, and I've had great results using it. And yes, once the disease is controlled, usually the clinical symptoms resolve as well, and in the case of his enormous appetite, getting that under control should cause him to lose the weight. Best of luck in getting this figured out.

My biggest concern is that your vet is talking about hyperadrenocorticism also known as Cushing's disease. This is what I think of when you discuss those symptoms, liver enzyme elevations and adrenal issues. Cushings is where they produce too much cortisol in their system. You can do a test to rule this in or out. You can have your vet do a low dose dexamethasone test OR a ACTH stimulation test. If it comes up positive then you can treat with the disease with a daily medicine called trilostane to help the symptoms. But you cannot cure cushings. I hope this helps and will help guide you in a conversation with your vet if this is actually what your vet thinks is going on.

According to the symptom of weight loss, otherwise normal and elevations on bloodwork, I would advise having your pet checked for Cushings disease (due to elevated ALP) via a specific test that your vet can go over with you. Also an abdominal ultrasound should be considered as well to check for any obvious masses since the Globulins were a bit high. Weight loss can also be caused by a change in diet as well, especially if your pet was once overweight, so its best to discuss this possibility with your vet as well. Also it is worth mentioning that none of the medications you listed would cause weight loss as an adverse effect. I do hope that things work out well for your pet moving forward. Best wishes and take care!

Just based on the information you described, I would probably consider testing for Cushing’s disease first, but it is possible to have both conditions so I would do the additional thyroid testing at the same time or soon after. Good catch!