The interaction between thyroxine (T4) and thyroxine-binding globulin (TBG) was examined in the serum of pregnant subjects and compared with that in normal serum. Serum T4, TBG capacity, and serum albumin concentrations were measured in serum from six normal and five pregnant subjects. The percent of free T4 (% free T4) was also measured by equilibrium dialysis against veronal buffer in which T4-binding by TBPA was completely abolished. Calculated values for the net equilibrium constant for the binding of T4 to TBG (KTBG) were significantly lower in serum from pregnant subjects (1.18 x 10(10) M-1) than in that from normal subjects (1.65 x 10(10) M-1). To assess the possibility that these findings were due to the presence of a dialyzable inhibitor of T4-binding in the serum from pregnant subjects, serum from normal subjects was dialyzed against that from pregnant subjects. In addition, serum from pregnant subjects was dialyzed against normal serum. KTBG was not altered after dialysis and no evidence of a dialyzable inhibitor of binding was found. The data suggest, therefore, that the TBG in the serum of pregnant women may have a lesser intrinsic affinity for T4 than that in normal serum.

Autoradiography↗

PubMedDate not supplied

Iodine-131 treatment of thyroid cancer: relation between effective half-life and efficacy of treatment.

The effective half-life (Teff) of radioactivity taken up by residual thyroid tumor after 131I therapy was measured and compared with response to treatment. Teff was determined from uptake by the lesions at four, eleven, and 18 days after 131I administration. The criterion for successful 131I therapy was that, in any successive 131I therapy, lesion uptake in the second therapy decreased to less than one-twentieth of that in the first therapy. In the 26 patients studied, 48 lesions were evaluated. Therapy was considered successful in 27 of these lesions and unsuccessful in 21. Mean Teff in the former was 2.48 +/- 0.93 days (mean +/- S.D.), significantly shorter than that in the latter, 5.70 +/- 2.62 days (p < 0.001). In some of the cases of solitary lesion, serum TSH levels, serum thyroglobulin values, and 131I protein bounded iodine (131I-PBI) were measured, but there were no significant differences between successful and unsuccessful therapy. The results of this study suggest that Teff seems to reflect the functional nature of the lesion and could be of prognostic value for the response to 131I therapy.

Adenocarcinoma, Follicular↗