Should my senior dog with low thyroid & Cushing's take meds?
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.
Updated on September 23rd, 2025