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  4. Speaking of thyroid, my patient’s TSH is normal, but T3 and T4 are low. Can you explain this a bit? I read one of your articles, but would love to hear it live.

Speaking of thyroid, my patient’s TSH is normal, but T3 and T4 are low. Can you explain this a bit? I read one of your articles, but would love to hear it live.

Chris Kresser: Okay. Amanda said, “Speaking of thyroid, my patient’s TSH is normal, but T3 and T4 are low. Can you explain this a bit? I read one of your articles, but would love to hear it live.”

Sure, and we’ll be going into excruciating detail on this later in the thyroid unit. There are some different possibilities there that can sometimes be an issue with sensitivity of cellular receptors to thyroid hormone. If it can be a conversion issue, it can be a nutrient deficiency issue. It also could just be related to the high variability of TSH. That’s something you really need to be aware of as a clinician. TSH has not only day-to-day variation, but it has a diurnal rhythm; not as significant as cortisol, which you expect to be very high in the morning and then low in the evening, but there is some diurnal variability with TSH, so testing in the morning might lead to a different value than testing in the evening. There is also the possibility where [for] someone in the initial stages of Hashimoto’s when that autoimmune disease is first starting, you get a relapsing remitting of the destruction of the thyroid gland, and that can lead to pretty dramatic and radical shifts in TSH and thyroid hormone.

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Usually, the first step to do when you see something that you don’t fully understand, like this, is to retest the whole panel. You’d also want to do, if you haven’t already, free T4 and free T3 and thyroid antibodies in that situation.

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