I had some thyroid testing done in May by my primary care doctor because my symptoms suggested possible hypothyroidism. The TSH was high and my doctor referred me to a reproductive endocrinologist because I’ve been trying to get pregnant for a year and she suspects my thyroid may have something to do with it. The fertility folks ran a TSH as part of my bloodwork, and it’s still high, so now they’re asking me to go back and get a full thyroid panel done. What is the rationale for repeating thyroid peroxidase antibody and antithyroglobulin antibody so soon after my previous tests? The T3 and T4 I can see changing over time, but the antibodies wouldn’t be different two months later, would they?
I asked my nurse that question via email and she responded “Please repeat. Our bodies can change.” Besides being somewhat condescending, it’s unhelpful. She knows I’m a med tech, but she’s talking to me like I’m a fifteen-year-old who doesn’t know what hormones or antibodies are.
I’ll repeat the tests, because I don’t want to be difficult and have them drop me for being a noncompliant patient, but I hate to be racking up extra testing costs and extra holes in my arms just because it’s the usual progression of testing and they make everyone do it.
It’s always reasonable to repeat an important lab test (to rule out various types of error and to get a hint about the trajectory). Indeed, I have seen various “outside” labs screw up thyroid antibody testing a number of times.
For anti-thyroid antibodies in particular, it’s possible that they may change titre rapidly in situations such as thyroiditis (an entity which can have a rather abrupt up and down course, and thus yield important prognostic information and therapeutic guidance, i.e. if the titres are markedly waning, the best approach may be to do nothing).
As an aside, there is some evidence that thyroid autoimmunity per se, and not just thyroid function, plays a role in the pathogenesis of female infertility. So, it may be useful to be quite certain of the existence (or absence) of thyroid autoimmunity in infertile women seeking to become pregnant (may guide therapy and inform prognosis).
Is the new testing with the same provider group? If not, the new group may want to get new testing with the lab they use and trust. My guess though is that the protocol for a new patient is a full work up, and it’s “easier” to repeat testing than deviate from the protocol. May be cheaper too, depending on how the tests are billed - panel vs individual tests. And if you’re going to get some of it done, it shouldn’t require any additional sticks, probably not any additional tubes, they’ll just run it off what they draw for the other tests.
Having said all that, don’t give up on getting your question answered. Keep asking. It generally behooves one to be a " difficult patient" as long as you remain polite.