A similar question from Trevor. “Thoughts on timing of lab draw for thyroid testing, since there seems to be a diurnal pattern associated with it. Is there a specific time of day you like to see the lab drawn?”
Chris: Usually if patients are taking their thyroid medication early in the morning and then getting a thyroid lab is a faster draw or a couple of hours after they’ve taken their medication is a good idea. But if you have situations where you’re seeing some weird stuff and things don’t make sense, you may also want to have them do a test later in the day, a couple of days later, just to get a different look at it.
It’s true that the results are diurnal, and it’s true that you’d probably get different readings at different times of day, but it’s also true that in almost all of the studies that have been done, thyroid lab values have just tested once a day and have not been really considered the diurnal rhythm of thyroid hormone in the testing procedure, and if you’re treating a patient over a period of time and you’re doing a test serially, I think in practice it’s not as much of an issue as we might assume generally. We are able to manage patients’ thyroid medication pretty well without worrying too much about that.