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. 1971 Jun;50(6):1187–1196. doi: 10.1172/JCI106596

The extrathyroidal conversion rate of thyroxine to triiodothyronine in normal man

Constance S Pittman 1, Joseph B Chambers Jr 1, Virginia H Read 1
PMCID: PMC292048  PMID: 5578229

Abstract

Eight normal subjects were administered tracer amounts of a 14C-labeled thyroxine, L-[tyrosyl-14C] T4, by multiple injections. Then serial blood samples were collected for isolation of the thyroxine, triiodothyronine, and tetraiodothyroacetic acid fractions by a combination of column and paper chromatographies. The chromatographic artifacts were corrected by adding to the sera a purified 3H-labeled thyroxine, D,L-[α,β-3H] T4 immediately after the separation of sera from blood. 1-2% of the serum 14C radioactivity was observed in the triiodothyronine fraction and 2-4% of the serum 14C radioactivity was observed in the tetraiodothyroacetic acid fraction. Complete kinetic studies of thyroxine and triiodothyronine were compared in the same individual in four of the subjects. The extrathyroidal conversion rates of thyroxine to triiodothyronine were calculated from data obtained during both the injection and the postinjection periods as functions of the 14C-labeled thyroxine and triiodothyronine remaining in the body at time t and their fractional turnover rates. The average daily rate of the extrathyroidal conversion of thyroxine to triiodothyronine was 4% of the extrathyroidal thyroxine pool or 33% of the total thyroxine production. The amount of triiodothyronine generated by this pathway (22 μg/day) was found to contribute 31% of the extrathyroidal triiodothyronine pool or 41% of the daily triiodothyronine production. This pathway is a major source of triiodothyronine production. The extrathyroidal conversions of thyroxine to triiodothyronine and tetraiodothyroacetic acid are major metabolic pathways of thyroxine in normal man.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. ALBRIGHT E. C., LARDY H. A., LARSON F. C., TOMITA K. Enzymatic conversion of thyroxine and triiodothyronine to the corresponding acetic acid analogues. Endocrinology. 1956 Aug;59(2):252–254. doi: 10.1210/endo-59-2-252. [DOI] [PubMed] [Google Scholar]
  2. ALBRIGHT E. C., LARSON F. C., TUST R. H. In vitro conversion of thyroxin to triiodothyronine by kidney slices. Proc Soc Exp Biol Med. 1954 May;86(1):137–140. doi: 10.3181/00379727-86-21031. [DOI] [PubMed] [Google Scholar]
  3. BERSON S. A., YALOW R. S. Quantitative aspects of iodine metabolism: the exchangeable organic iodine pool, and the rates of thyroidal secretion, peripheral degradation and fecal excretion, of endogenously synthesized organically bound iodine. J Clin Invest. 1954 Nov;33(11):1533–1552. doi: 10.1172/JCI103032. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Bellabarba D., Peterson R. E., Sterling K. An improved method for chromatography of iodothyronines. J Clin Endocrinol Metab. 1968 Feb;28(2):305–307. doi: 10.1210/jcem-28-2-305. [DOI] [PubMed] [Google Scholar]
  5. Bellabarba D., Sterling K. Formation of ester of thyroxine and triiodothyronine during alcoholic extraction. J Clin Endocrinol Metab. 1969 Nov;29(11):1510–1513. doi: 10.1210/jcem-29-11-1510. [DOI] [PubMed] [Google Scholar]
  6. Braverman L. E., Ingbar S. H., Sterling K. Conversion of thyroxine (T4) to triiodothyronine (T3) in athyreotic human subjects. J Clin Invest. 1970 May;49(5):855–864. doi: 10.1172/JCI106304. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. GALTON V. A., PITT-RIVERS R. The identification of the acetic acid analogues of thyroxine and tri-iodothyronine in mammalian tissues. Biochem J. 1959 Jun;72(2):319–321. doi: 10.1042/bj0720319. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. GREEN W. L., INGBAR S. H. The peripheral metabolism of tri- and tetraiodothyroacetic acids in man. J Clin Endocrinol Metab. 1961 Dec;21:1548–1565. doi: 10.1210/jcem-21-12-1548. [DOI] [PubMed] [Google Scholar]
  9. GROSS J., PITT-RIVERS R. The identification of 3:5:3'-L-triiodothyronine in human plasma. Lancet. 1952 Mar 1;1(6705):439–441. doi: 10.1016/s0140-6736(52)91952-1. [DOI] [PubMed] [Google Scholar]
  10. Hollander C. S. On the nature of the circulating thyroid hormone: clinical studies of triiodothyronine and thyroxine in serum using gas chromatographic methods. Trans Assoc Am Physicians. 1968;81:76–91. [PubMed] [Google Scholar]
  11. INGBAR S. H., FREINKEL N. Simultaneous estimation of rates of thyroxine degradation and thyroid hormone synthesis. J Clin Invest. 1955 Jun;34(6):808–819. doi: 10.1172/JCI103136. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Inoue K., Grimm Y., Greer M. A. Quantitative studies on the iodinated components secreted by the rat thyroid gland as determined by in situ perfusion. Endocrinology. 1967 Nov;81(5):946–964. doi: 10.1210/endo-81-5-946. [DOI] [PubMed] [Google Scholar]
  13. LASSITER W. R., STANBURY J. B. The in vivo conversion of thyroxine to 3:5:3'triiodothyronine. J Clin Endocrinol Metab. 1958 Aug;18(8):903–906. doi: 10.1210/jcem-18-8-903. [DOI] [PubMed] [Google Scholar]
  14. MURPHY B. E., PATTEE C. J. DETERMINATION OF THYROXINE UTILIZING THE PROPERTY OF PROTEIN-BINDING. J Clin Endocrinol Metab. 1964 Feb;24:187–196. doi: 10.1210/jcem-24-2-187. [DOI] [PubMed] [Google Scholar]
  15. Nauman J. A., Nauman A., Werner S. C. Total and free triiodothyronine in human serum. J Clin Invest. 1967 Aug;46(8):1346–1355. doi: 10.1172/JCI105627. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. PITT-RIVERS R., STANBURY J. B., RAPP B. Conversion of thyroxine to 3-5-3'-triiodothyronine in vivo. J Clin Endocrinol Metab. 1955 May;15(5):616–620. doi: 10.1210/jcem-15-5-616. [DOI] [PubMed] [Google Scholar]
  17. Pittman C. S., Read V. H., Chambers J. B., Jr, Nakafuji H. The integrity of the ether linkage during thyroxine metabolism in man. J Clin Invest. 1970 Feb;49(2):373–380. doi: 10.1172/JCI106246. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. ROCHE J., MICHEL R., TATA J. Sur la nature des combinaisons iodées excrétées par le foie et le rein après administration de L-thyroxine et de L-3:5:3'-triiodothyronine. Biochim Biophys Acta. 1954 Dec;15(4):500–507. doi: 10.1016/0006-3002(54)90007-4. [DOI] [PubMed] [Google Scholar]
  19. STANBURY J. B. Deiodination of the iodinated amino acids. Ann N Y Acad Sci. 1960 Apr 23;86:417–439. doi: 10.1111/j.1749-6632.1960.tb42820.x. [DOI] [PubMed] [Google Scholar]
  20. STERLING K., CHODOS R. B. Radiothyroxine turnover studies in myxedema, thyrotoxicosis, and hypermetabolism without endocrine disease. J Clin Invest. 1956 Jul;35(7):806–813. doi: 10.1172/JCI103333. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Sterling K., Bellabarba D., Newman E. S., Brenner M. A. Determination of triiodothyronine concentration in human serum. J Clin Invest. 1969 Jun;48(6):1150–1158. doi: 10.1172/JCI106072. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Surks M. I., Oppenheimer J. H. Formation of iodoprotein during the peripheral metabolism of 3,5,3'-triiodo-L-thyronine-125I in the euthyroid man and rat. J Clin Invest. 1969 Apr;48(4):685–695. doi: 10.1172/JCI106026. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. TAUROG A., PORTER J. C., THIO D. T. NATURE OF THE 131-I-COMPOUNDS RELEASED INTO THE THYROID VEINS OF RABBITS, DOGS AND CATS, BEFORE AND AFTER TSH ADMINISTRATION. Endocrinology. 1964 Jun;74:902–913. doi: 10.1210/endo-74-6-902. [DOI] [PubMed] [Google Scholar]
  24. VOLPERT E. M., GRINBERG R., WERNER S. C. METABOLISM OF LABELLED THYROID HORMONE BY THYROTROPIC AND ADRENOTROPIC MOUSE PITUITARY TUMORS. Acta Unio Int Contra Cancrum. 1964;20:1137–1140. [PubMed] [Google Scholar]
  25. Woeber K. A., Sobel R. J., Ingbar S. H., Sterling K. The peripheral metabolism of triiodothyronine in normal subjects and in patients with hyperthyroidism. J Clin Invest. 1970 Apr;49(4):643–649. doi: 10.1172/JCI106275. [DOI] [PMC free article] [PubMed] [Google Scholar]

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