Why is Canine Hypothyroidism Difficult to Diagnose?

Diane Levitan, VMD, DACVIM, from Peace Love Pets Veterinary Care, explains why canine hypothyroidism is difficult to diagnose.

Interview Transcript (slightly modified for readability)

"Hypothyroidism is a very difficult disease to diagnose. It seems so straighforward, but it's really not and that's because there are some things that a lot of people don't really understand, particularly that [thyroxine] t4 or the thyroid level in a dog tends to go down with their age. So, when people find a dog that's 10 or 11 years old that has a very low thyroid level, it can be misinterpreted as very low where it's actually normal for that dog's age. So, that is one thing that will really make it very difficult to accurately diagnose hypothyroidism.

Another point is that as dogs get older, they get a little less active and they tend to gain weight and so, when they gain weight, and their thyroid levels are a little lower, that gives people even more thought that maybe this animal has the disease, when, in fact, it's very unlikely for a dog over 8 or 9 years old to become hypothyroid."