Oscillations in the rate of disappearance of labeled triiodothyronine from human plasma and the minimum sampling rate for their observation
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Oscillations in the rate of disappearance of labeled-T3 have been observed in this experiment. A 4-h sampling period is insufficient to demonstrate this behavior; and sampling every 2 h appears to be an approximate upper limit on the sampling period. A more detailed knowledge of the character of these oscillations may be obtained by sampling more often than every 2 h during time intervals when the variations are largest. Curve A in Figure 2 suggests that sampling every hour during the mid-day would be desirable.
The results about T3 reported here are not necessarily incompatible with reports that thyroxine (T4) concentration may not be diurnal, as discussed in the introduction. Although T3 and T4 are almost the same species, to within a single atom, their dynamics of distribution, binding and metabolism are sufficiently different 6 for one to be observedly diurnal and the other not. Another possibility is that diurnal variations may exist in T4 disappearance which arc too small to measure by currently available techniques.
KeywordsDiurnal Variation Triiodothyronine Methimazole Plasma Thyroxine FENSON
Des oscillations dans la réduction du taux de triiodothyronine (marquée125I) ont été observées dans le plasma humain. On a trouvé qu'une période d'échantillonage de 4 h était insuffisante pour révéler ces oscillations. Une période de 2 h constituerait une limite supérieure adéquate.