The role of glucocorticoids in the stress-induced reduction of extrathyroidal 3,5,3'-triiodothyronine generation in rats

A. C. Bianco, M. T. Nunes, N. S. Hell, R. M B Maciel

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Abstract

Serum concentrations of T4, T3, and rT3 as well as liver and kidney 5'-deiodinase activity, have been examined in rats stressed by restraint. After immobilization, serum concentrations of T3 decreased significantly (6 hr, -33 ± 1%; 8 h, -42 ± 3%), while serum rT3 increased (6 h, +55 ± 3%; 8 h, +75 ± 5%). In the same or similarly treated animals, there was a time-dependent reduction in T4 5'-deiodinase activity in both liver (4 h, -23 ± 2%; 8 h, -43 ± 3%) and kidney (4 h, -18 ± 1%; 8 h, -42 ± 3%) homogenates. The reduction in hepatic and renal T3 production was due to reduced enzyme activity and not to reduced substrate availability. In spite of reductions in serum TSH (4 h, -9 ± 1%; 8 h, -51 ± 5%), the serum T4 concentration did not fall. The serum concentration of corticosterone reached 30 times the basal level after 8 h of restraint. Either adrenalectomy or metyrapone treatment, followed by replacement with nonstress doses of B, completely prevented the alterations of iodothyronine metabolism induced by restraint. These results indicate that the stress-induced elevation of plasma glucorticoids plays a key role in the pathogenesis of the low T3 syndrome in this model. The reduction in serum T3 may be accounted for by a reduction in T3 production by liver and kidney, adding support to the concept that these organs are an important source of plasma T3 in the rat.

Original languageEnglish
Pages (from-to)1033-1038
Number of pages6
JournalEndocrinology
Volume120
Issue number3
StatePublished - Jan 1 1987

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

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    Bianco, A. C., Nunes, M. T., Hell, N. S., & Maciel, R. M. B. (1987). The role of glucocorticoids in the stress-induced reduction of extrathyroidal 3,5,3'-triiodothyronine generation in rats. Endocrinology, 120(3), 1033-1038.