Even though only a small amount of iodoprotein is made after giving T3, it holds onto radioactive iodine for several days and becomes the main source of detectable radioactivity in the blood during that time.
Evidence from Studies
No evidence studies found yet.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
A systematic review could determine whether iodoprotein consistently accounts for a large proportion of plasma radioactivity after T3 administration across multiple tracer studies.
A systematic review and meta-analysis of all published T3 tracer studies (n≥10) measuring iodoprotein-bound radioactivity over 7 days, standardizing methods to quantify its contribution as a percentage of total plasma radioactivity.
An RCT could test whether blocking iodoprotein formation alters radioactivity kinetics, but this is not feasible in healthy humans.
A double-blind RCT administering [125I]T3 to 40 healthy adults, with one group receiving an inhibitor of iodoprotein synthesis and the other placebo, measuring plasma radioactivity distribution over 72 hours.
A cohort could correlate iodoprotein levels with thyroid hormone clearance rates, but this study does not assess clearance.
A prospective cohort of 150 healthy adults receiving [125I]T3, with serial plasma sampling to measure iodoprotein-bound radioactivity and correlate it with T3 clearance half-life.
A cross-sectional study could measure iodoprotein levels after T3 injection, but cannot resolve kinetics.
A cross-sectional study measuring iodoprotein-bound radioactivity at 24, 48, and 72 hours after [125I]T3 injection in 100 healthy adults using radioimmunoassay and chromatography.
A case report could describe abnormal iodoprotein accumulation in a patient with impaired hormone clearance.
A case series of 5 patients with thyroid hormone resistance or impaired deiodination, receiving [125I]T3 and measuring prolonged iodoprotein radioactivity compared to healthy controls.