Why is Hypothyroidism Easily Misdiagnosed?

Diane Levitan, VMD, DACVIM, from Peace Love Pets Veterinary Care, explains why hypothyroidism is so easily misdiagnosed.

Interview Transcript (slightly modified for readability)

“Hypothyroidism is a very easy disease to misdiagnose, and the reason is because the testing that we have available to us can make it confusing. Sometimes it’s very straightforward, but sometimes we get confused between the different modalities of testing that we have available to us. We need to really be careful how we interpret those numbers and understand that as animals age, their thyroid levels and their TSH levels will decline, and that’s a normal process. Gaining weight as you get older is also a normal process.

Those are the things that [veterinarians] are particularly looking at to help us diagnose hypothyroidism. If we go only by those few tests, we may make a mistake; there are other tests that are available that [veterinarians] really need to learn how to use to most accurately diagnose this problem.

Typically, we’ll use blood tests to help us determine if, in fact, an animal is hypothyroid. We’ll do a thyroid total T4, which is a total T4 value of type of thyroid hormone. We’ll use Free T4, as well as a TSH. The TSH is an assay that is not perfect for dogs and cats as it is [for] people, but it can be extremely helpful in discerning whether or not [a pet has] hypothyroidism, and the key is really to properly interpret T4, Free T4, and TSH in light of your patient’s clinical signs.”