par Mc Guire, Robert R.A.;Glinoer, Daniel 
;Albert, Michael M.A.;Robb, J.
Référence Endocrinology, 110, 4, page (1340-1346)
Publication Publié, 1982
;Albert, Michael M.A.;Robb, J.Référence Endocrinology, 110, 4, page (1340-1346)
Publication Publié, 1982
Article révisé par les pairs
| Résumé : | The metabolism of T4-binding globulin (TBG) was studied in rhesus monkeys after the iv injection of 125I-labeled TBG. Two sets of three animals were used. Three normal animals were studied before and 18, 38, and 53 days after the onset of T4 (125 μg/day) treatment. Three thyroidectomized animals from a prior study were studied before and during replacement therapy with T3 or T4. Serum TBG (by RIA), serum [125I]PBI, and daily urinary 125I measurements were analyzed using a three-compartment kinetic model developed previously. During the euthyroid period, serum TBG was 18.1 ± 0.9 μg/ml (mean ± SEM), the total distribution volume was 436 ± 18 ml/3 kg BW, the final decay rate (k) was 0.27 ± 0.01 day-1, the MCR was 113 ± 8 ml/3 kg ·day, and the production rate (PR) was 2.05 ± 0.10 mg/3 kg ·day; all agreed well with prior studies.During T4-induced hyperthyroidism, serum TBG and total distribution volume did not change significantly; the transient drop in serum TBG during the first week seen previously with T3-induced hyperthyroidism did not occur. The k value did not change after 1 week, but increased steadily from 22% above control after 18 days to 52% above control after 53 days. MCR and PR also increased by 82% and 65%, respectively, after 38 days of T4 treatment, in contrast to the decrease seen previously with T3.In the three thyroidectomized animals, both T3 and T4 replacement restored serum TBG and k to euthyroid levels. Replacement T3, however, in contrast to T4, failed to elevate either MCR or PR to normal. The basis for the different responses to T4 and T3 is not clear, but they may reflect different effects on the release of TBG from hepatocytes. © 1982 by The Endocrine Society. |
